diff --git a/src/jvm/build.gradle.kts b/src/jvm/build.gradle.kts
index e8203b5..e70d4b1 100644
--- a/src/jvm/build.gradle.kts
+++ b/src/jvm/build.gradle.kts
@@ -3,9 +3,11 @@ import com.vanniktech.maven.publish.JavadocJar
 import com.vanniktech.maven.publish.SourcesJar
 import me.champeau.gradle.japicmp.JapicmpTask
 import net.ltgt.gradle.errorprone.errorprone
+import org.gradle.testing.jacoco.tasks.JacocoReport
 
 plugins {
     `java-library`
+    jacoco
     alias(libs.plugins.maven.publish)
     alias(libs.plugins.japicmp)
     alias(libs.plugins.spotless)
@@ -39,10 +41,27 @@ val testJdk = providers.gradleProperty("testJdk").map(String::toInt).getOrElse(2
 tasks.withType<Test>().configureEach {
     useJUnitPlatform()
     javaLauncher.set(javaToolchains.launcherFor { languageVersion = JavaLanguageVersion.of(testJdk) })
+    finalizedBy(tasks.named("jacocoTestReport"))
 }
 
+tasks.named<JacocoReport>("jacocoTestReport") {
+    dependsOn(tasks.named("test"))
+    reports {
+        xml.required = true
+        html.required = true
+    }
+}
+
+tasks.named("check") { dependsOn("jacocoTestReport") }
+
 dependencies {
     api(libs.jspecify)
+    implementation(libs.classgraph)
+    api(libs.jackson.databind)
+    implementation(libs.jackson.datatype.jsr310)
+    implementation(libs.approvaltests)
+    implementation(platform(libs.junit.bom))
+    implementation(libs.junit.jupiter)
     errorprone(libs.errorprone.core)
     errorprone(libs.errorprone.contrib)
     errorprone(libs.errorprone.refaster)
diff --git a/src/jvm/gradle/libs.versions.toml b/src/jvm/gradle/libs.versions.toml
index 062ae3c..054c966 100644
--- a/src/jvm/gradle/libs.versions.toml
+++ b/src/jvm/gradle/libs.versions.toml
@@ -2,6 +2,9 @@
 kotlin = "2.3.21"
 scala = "3.8.3"
 jspecify = "1.0.0"
+jackson = "2.17.0"
+classgraph = "4.8.179"
+approvaltests = "24.0.0"
 junit = "5.12.2"
 spotless = "8.6.0"
 palantir-java-format = "2.91.0"
@@ -14,6 +17,10 @@ nullaway-plugin = "3.0.0"
 
 [libraries]
 jspecify = { module = "org.jspecify:jspecify", version.ref = "jspecify" }
+classgraph = { module = "io.github.classgraph:classgraph", version.ref = "classgraph" }
+jackson-databind = { module = "com.fasterxml.jackson.core:jackson-databind", version.ref = "jackson" }
+jackson-datatype-jsr310 = { module = "com.fasterxml.jackson.datatype:jackson-datatype-jsr310", version.ref = "jackson" }
+approvaltests = { module = "com.approvaltests:approvaltests", version.ref = "approvaltests" }
 scala-library = { module = "org.scala-lang:scala3-library_3", version.ref = "scala" }
 scalatest = { module = "org.scalatest:scalatest_3", version = "3.2.19" }
 junit-bom = { module = "org.junit:junit-bom", version.ref = "junit" }
diff --git a/src/jvm/src/main/java/io/eventdriven/strictland/Contract.java b/src/jvm/src/main/java/io/eventdriven/strictland/Contract.java
new file mode 100644
index 0000000..4f714c7
--- /dev/null
+++ b/src/jvm/src/main/java/io/eventdriven/strictland/Contract.java
@@ -0,0 +1,47 @@
+package io.eventdriven.strictland;
+
+import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.databind.json.JsonMapper;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+
+/**
+ * Entry point for the contract DSL used to verify event schema versioning and serialization compatibility.
+ */
+public class Contract {
+    private static final ObjectMapper DEFAULT_MAPPER = new JsonMapper()
+            .registerModule(new JavaTimeModule())
+            .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
+            .configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
+
+    private final ObjectMapper mapper;
+
+    private Contract(ObjectMapper mapper) {
+        this.mapper = mapper;
+    }
+
+    public static Contract specification() {
+        return new Contract(DEFAULT_MAPPER);
+    }
+
+    public static Contract specification(ObjectMapper mapper) {
+        return new Contract(mapper);
+    }
+
+    public <S> GivenStep<S> given(Snapshot.ByClass<S> snapshot) {
+        return new GivenStep<>(snapshot, null, mapper);
+    }
+
+    public GivenStep<Object> given(Snapshot.ByMessageType snapshot) {
+        return new GivenStep<>(snapshot, null, mapper);
+    }
+
+    public GivenStep<Object> given(Snapshot.ByPath snapshot) {
+        return new GivenStep<>(snapshot, null, mapper);
+    }
+
+    public <S> GivenStep<S> given(S instance) {
+        return new GivenStep<>(null, instance, mapper);
+    }
+}
diff --git a/src/jvm/src/main/java/io/eventdriven/strictland/GivenStep.java b/src/jvm/src/main/java/io/eventdriven/strictland/GivenStep.java
new file mode 100644
index 0000000..bda2f9a
--- /dev/null
+++ b/src/jvm/src/main/java/io/eventdriven/strictland/GivenStep.java
@@ -0,0 +1,41 @@
+package io.eventdriven.strictland;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.jspecify.annotations.Nullable;
+
+/**
+ * The "given" step of the contract DSL, holding either a snapshot or an instance to work with.
+ */
+public class GivenStep<S> {
+    final @Nullable Snapshot snapshot;
+    final @Nullable S instance;
+    final ObjectMapper mapper;
+
+    GivenStep(@Nullable Snapshot snapshot, @Nullable S instance, ObjectMapper mapper) {
+        this.snapshot = snapshot;
+        this.instance = instance;
+        this.mapper = mapper;
+    }
+
+    public ThenContractStep<S> whenSerialized() {
+        var instance = requireInstance();
+        return new ThenContractStep<>(instance, null, mapper);
+    }
+
+    public ThenContractStep<S> whenSerialized(Snapshot destination) {
+        var instance = requireInstance();
+        return new ThenContractStep<>(instance, destination, mapper);
+    }
+
+    private S requireInstance() {
+        if (instance == null) {
+            throw new IllegalStateException(
+                    "whenSerialized() requires an instance — use Contract.given(instance), not Contract.given(Snapshot)");
+        }
+        return instance;
+    }
+
+    public <T> ThenCompatibilityStep<S, T> whenDeserializedAs(Class<T> targetType) {
+        return new ThenCompatibilityStep<>(snapshot, instance, targetType, mapper);
+    }
+}
diff --git a/src/jvm/src/main/java/io/eventdriven/strictland/PublicApiScanner.java b/src/jvm/src/main/java/io/eventdriven/strictland/PublicApiScanner.java
new file mode 100644
index 0000000..61f1682
--- /dev/null
+++ b/src/jvm/src/main/java/io/eventdriven/strictland/PublicApiScanner.java
@@ -0,0 +1,123 @@
+package io.eventdriven.strictland;
+
+import io.github.classgraph.ClassGraph;
+import io.github.classgraph.ClassInfo;
+import java.lang.reflect.*;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.function.Predicate;
+import java.util.stream.Collectors;
+
+public class PublicApiScanner {
+    private final String packageName;
+    private Predicate<Method> methodFilter = m -> true;
+    private boolean excludeConstructors;
+
+    private PublicApiScanner(String packageName) {
+        this.packageName = packageName;
+    }
+
+    public static PublicApiScanner forPackage(String packageName) {
+        return new PublicApiScanner(packageName);
+    }
+
+    public PublicApiScanner excludingMethods(Predicate<Method> filter) {
+        this.methodFilter = this.methodFilter.and(filter.negate());
+        return this;
+    }
+
+    public PublicApiScanner excludeConstructors() {
+        this.excludeConstructors = true;
+        return this;
+    }
+
+    public PublicApiScanner onlyGettersAndFields() {
+        return excludeConstructors()
+                .excludeStandardObjectMethods()
+                .excludingMethods(m -> m.getParameterCount() > 0 || m.getReturnType() == void.class);
+    }
+
+    public PublicApiScanner excludeStandardObjectMethods() {
+        return excludingMethods(m -> (m.getName().equals("equals") && m.getParameterCount() == 1)
+                || (m.getName().equals("hashCode") && m.getParameterCount() == 0)
+                || (m.getName().equals("toString") && m.getParameterCount() == 0));
+    }
+
+    public String generate() {
+        try (var scanResult =
+                new ClassGraph().enableAllInfo().acceptPackages(packageName).scan()) {
+
+            return scanResult.getAllClasses().stream()
+                    .map(ClassInfo::loadClass)
+                    .filter(c -> Modifier.isPublic(c.getModifiers()))
+                    .sorted(Comparator.comparing(Class::getName))
+                    .map(this::describeType)
+                    .collect(Collectors.joining("\n\n"));
+        }
+    }
+
+    private String describeType(Class<?> clazz) {
+        var sb = new StringBuilder();
+        sb.append(typeDeclaration(clazz)).append(" {\n");
+
+        Arrays.stream(clazz.getDeclaredFields())
+                .filter(f -> Modifier.isPublic(f.getModifiers()) && !f.isSynthetic())
+                .sorted(Comparator.comparing(Field::getName))
+                .forEach(f -> sb.append("  ").append(f.toGenericString()).append(";\n"));
+
+        if (!excludeConstructors) {
+            Arrays.stream(clazz.getDeclaredConstructors())
+                    .filter(c -> Modifier.isPublic(c.getModifiers()))
+                    .sorted(Comparator.comparing(Constructor::toGenericString))
+                    .forEach(c -> sb.append("  ").append(formatConstructor(c)).append(";\n"));
+        }
+
+        Arrays.stream(clazz.getDeclaredMethods())
+                .filter(m -> Modifier.isPublic(m.getModifiers()) && !m.isSynthetic() && !m.isBridge())
+                .filter(methodFilter)
+                .sorted(Comparator.comparing(Method::getName).thenComparing(Method::toGenericString))
+                .forEach(m -> sb.append("  ").append(formatMethod(m)).append(";\n"));
+
+        sb.append("}");
+        return sb.toString();
+    }
+
+    private static String formatConstructor(Constructor<?> c) {
+        var params = Arrays.stream(c.getGenericParameterTypes())
+                .map(Type::getTypeName)
+                .collect(Collectors.joining(", "));
+        return Modifier.toString(c.getModifiers()) + " " + c.getDeclaringClass().getSimpleName() + "(" + params + ")";
+    }
+
+    private static String formatMethod(Method m) {
+        var params = Arrays.stream(m.getGenericParameterTypes())
+                .map(Type::getTypeName)
+                .collect(Collectors.joining(", "));
+        return Modifier.toString(m.getModifiers()) + " "
+                + m.getGenericReturnType().getTypeName() + " " + m.getName() + "(" + params + ")";
+    }
+
+    private static String typeDeclaration(Class<?> clazz) {
+        var parts = new StringBuilder();
+
+        if (Modifier.isPublic(clazz.getModifiers())) parts.append("public ");
+        if (Modifier.isStatic(clazz.getModifiers())) parts.append("static ");
+        if (Modifier.isFinal(clazz.getModifiers()) && !clazz.isEnum()) parts.append("final ");
+
+        if (clazz.isRecord()) parts.append("record");
+        else if (clazz.isInterface()) parts.append("interface");
+        else if (clazz.isEnum()) parts.append("enum");
+        else parts.append("class");
+
+        parts.append(" ").append(clazz.getName());
+
+        var interfaces = clazz.getInterfaces();
+        if (interfaces.length > 0) {
+            var keyword = clazz.isInterface() ? " extends " : " implements ";
+            parts.append(keyword)
+                    .append(Arrays.stream(interfaces).map(Class::getName).collect(Collectors.joining(", ")));
+        }
+
+        return parts.toString();
+    }
+}
diff --git a/src/jvm/src/main/java/io/eventdriven/strictland/Snapshot.java b/src/jvm/src/main/java/io/eventdriven/strictland/Snapshot.java
new file mode 100644
index 0000000..2274c84
--- /dev/null
+++ b/src/jvm/src/main/java/io/eventdriven/strictland/Snapshot.java
@@ -0,0 +1,36 @@
+package io.eventdriven.strictland;
+
+import java.nio.file.Path;
+import org.jspecify.annotations.Nullable;
+
+/**
+ * Identifies the source of an approved snapshot used to verify schema contracts and compatibility.
+ */
+public sealed interface Snapshot permits Snapshot.ByClass, Snapshot.ByMessageType, Snapshot.ByPath {
+
+    record ByClass<T>(Class<T> sourceType) implements Snapshot {}
+
+    record ByMessageType(String messageType, @Nullable Class<?> sourceType) implements Snapshot {}
+
+    record ByPath(Path path, @Nullable Class<?> sourceType) implements Snapshot {}
+
+    static <T> ByClass<T> of(Class<T> sourceType) {
+        return new ByClass<>(sourceType);
+    }
+
+    static ByPath at(Path path) {
+        return new ByPath(path, null);
+    }
+
+    static <T> ByPath at(Path path, Class<T> sourceType) {
+        return new ByPath(path, sourceType);
+    }
+
+    static ByMessageType forMessageType(String messageType) {
+        return new ByMessageType(messageType, null);
+    }
+
+    static <T> ByMessageType forMessageType(String messageType, Class<T> sourceType) {
+        return new ByMessageType(messageType, sourceType);
+    }
+}
diff --git a/src/jvm/src/main/java/io/eventdriven/strictland/SnapshotPathResolver.java b/src/jvm/src/main/java/io/eventdriven/strictland/SnapshotPathResolver.java
new file mode 100644
index 0000000..265d204
--- /dev/null
+++ b/src/jvm/src/main/java/io/eventdriven/strictland/SnapshotPathResolver.java
@@ -0,0 +1,29 @@
+package io.eventdriven.strictland;
+
+import java.nio.file.Path;
+import java.util.Set;
+
+class SnapshotPathResolver {
+    private static final Set<String> DSL_CLASSES = Set.of(
+            Contract.class.getName(),
+            GivenStep.class.getName(),
+            ThenContractStep.class.getName(),
+            ThenCompatibilityStep.class.getName(),
+            SnapshotPathResolver.class.getName());
+    private static final String SOURCE_ROOT = "src/test/java";
+
+    static Path resolve(String snapshotName) {
+        var callerClass = StackWalker.getInstance(StackWalker.Option.RETAIN_CLASS_REFERENCE)
+                .walk(frames -> frames.filter(f -> !DSL_CLASSES.contains(f.getClassName()))
+                        .filter(f -> !f.getClassName().startsWith("java."))
+                        .filter(f -> !f.getClassName().startsWith("jdk."))
+                        .filter(f -> !f.getClassName().startsWith("sun."))
+                        .filter(f -> !f.getClassName().startsWith("org.junit."))
+                        .findFirst()
+                        .orElseThrow(() -> new IllegalStateException("Cannot determine calling test class from stack")))
+                .getDeclaringClass();
+
+        var packagePath = callerClass.getPackageName().replace('.', '/');
+        return Path.of(SOURCE_ROOT, packagePath, snapshotName + ".approved.txt");
+    }
+}
diff --git a/src/jvm/src/main/java/io/eventdriven/strictland/ThenCompatibilityStep.java b/src/jvm/src/main/java/io/eventdriven/strictland/ThenCompatibilityStep.java
new file mode 100644
index 0000000..344ac8e
--- /dev/null
+++ b/src/jvm/src/main/java/io/eventdriven/strictland/ThenCompatibilityStep.java
@@ -0,0 +1,109 @@
+package io.eventdriven.strictland;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.fail;
+
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.function.Consumer;
+import org.jspecify.annotations.Nullable;
+
+/**
+ * The "then" step of the contract DSL that verifies forward and backward compatibility of deserialization.
+ */
+public class ThenCompatibilityStep<S, T> {
+    private final @Nullable Snapshot snapshot;
+    private final @Nullable S instance;
+    private final Class<T> targetType;
+    private final ObjectMapper mapper;
+
+    ThenCompatibilityStep(@Nullable Snapshot snapshot, @Nullable S instance, Class<T> targetType, ObjectMapper mapper) {
+        this.snapshot = snapshot;
+        this.instance = instance;
+        this.targetType = targetType;
+        this.mapper = mapper;
+    }
+
+    public void thenForwardCompatible() {
+        verifySharedFields(t -> {});
+    }
+
+    public void thenForwardCompatible(Consumer<T> extra) {
+        verifySharedFields(extra);
+    }
+
+    public void thenBackwardCompatible() {
+        verifySharedFields(t -> {});
+    }
+
+    public void thenBackwardCompatible(Consumer<T> extra) {
+        verifySharedFields(extra);
+    }
+
+    private void verifySharedFields(Consumer<T> extra) {
+        var sourceBytes = resolveSourceBytes();
+        T deserialized;
+        try {
+            deserialized = mapper.readValue(sourceBytes, targetType);
+        } catch (IOException e) {
+            throw new RuntimeException("Deserialization as " + targetType.getSimpleName() + " failed", e);
+        }
+        if (deserialized == null) {
+            fail("Deserialization as " + targetType.getSimpleName() + " returned empty");
+            return;
+        }
+        assertSharedFieldsMatch(sourceBytes, deserialized);
+        extra.accept(deserialized);
+    }
+
+    private void assertSharedFieldsMatch(byte[] sourceBytes, T target) {
+        try {
+            var sourceMap = toMap(sourceBytes);
+            var targetMap = toMap(mapper.writeValueAsBytes(target));
+
+            var sharedKeys = new HashSet<>(sourceMap.keySet());
+            sharedKeys.retainAll(targetMap.keySet());
+
+            for (var key : sharedKeys) {
+                assertEquals(
+                        sourceMap.get(key), targetMap.get(key), "Field '" + key + "' value differs between versions");
+            }
+        } catch (IOException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private Map<String, Object> toMap(byte[] bytes) throws IOException {
+        return mapper.readValue(bytes, new TypeReference<>() {});
+    }
+
+    private byte[] resolveSourceBytes() {
+        if (instance != null) {
+            try {
+                return mapper.writeValueAsBytes(instance);
+            } catch (IOException e) {
+                throw new RuntimeException(
+                        "Serialization of " + instance.getClass().getSimpleName() + " failed", e);
+            }
+        }
+        if (snapshot == null) {
+            throw new IllegalStateException("Either a snapshot or an instance is required");
+        }
+        var path =
+                switch (snapshot) {
+                    case Snapshot.ByClass<?> s ->
+                        SnapshotPathResolver.resolve(s.sourceType().getSimpleName());
+                    case Snapshot.ByMessageType s -> SnapshotPathResolver.resolve(s.messageType());
+                    case Snapshot.ByPath s -> s.path();
+                };
+        try {
+            return Files.readAllBytes(path);
+        } catch (IOException e) {
+            throw new RuntimeException("Cannot read snapshot file: " + path, e);
+        }
+    }
+}
diff --git a/src/jvm/src/main/java/io/eventdriven/strictland/ThenContractStep.java b/src/jvm/src/main/java/io/eventdriven/strictland/ThenContractStep.java
new file mode 100644
index 0000000..e5eafb5
--- /dev/null
+++ b/src/jvm/src/main/java/io/eventdriven/strictland/ThenContractStep.java
@@ -0,0 +1,87 @@
+package io.eventdriven.strictland;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import java.io.File;
+import java.nio.file.Path;
+import org.approvaltests.Approvals;
+import org.approvaltests.core.Options;
+import org.approvaltests.namer.ApprovalNamer;
+import org.approvaltests.reporters.AutoApproveWhenEmptyReporter;
+import org.jspecify.annotations.Nullable;
+
+/**
+ * The "then" step of the contract DSL that verifies the serialized shape of an instance is unchanged.
+ */
+public class ThenContractStep<S> {
+    private final S instance;
+    private final @Nullable Snapshot destination;
+    private final ObjectMapper mapper;
+
+    ThenContractStep(S instance, @Nullable Snapshot destination, ObjectMapper mapper) {
+        this.instance = instance;
+        this.destination = destination;
+        this.mapper = mapper;
+    }
+
+    public void thenContractIsUnchanged() {
+        verify(destination != null ? optionsFor(destination) : defaultOptions());
+    }
+
+    private Options defaultOptions() {
+        return new Options().forFile().withBaseName(instance.getClass().getSimpleName());
+    }
+
+    private Options optionsFor(Snapshot s) {
+        return switch (s) {
+            case Snapshot.ByClass<?> b ->
+                new Options().forFile().withBaseName(b.sourceType().getSimpleName());
+            case Snapshot.ByMessageType b -> new Options().forFile().withBaseName(b.messageType());
+            case Snapshot.ByPath b -> new Options().forFile().withNamer(namedAt(b.path()));
+        };
+    }
+
+    private void verify(Options options) {
+        try {
+            Approvals.verify(
+                    mapper.writeValueAsString(instance), options.withReporter(new AutoApproveWhenEmptyReporter()));
+        } catch (JsonProcessingException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private static ApprovalNamer namedAt(Path path) {
+        var parent = path.getParent();
+        if (parent == null) {
+            throw new IllegalArgumentException("Snapshot path must have a parent directory: " + path);
+        }
+        var directory = parent.toAbsolutePath() + File.separator;
+        var name = path.getFileName().toString().replaceAll("\\.approved\\.txt$", "");
+        return new ApprovalNamer() {
+            @Override
+            public String getApprovalName() {
+                return name;
+            }
+
+            @Override
+            public String getSourceFilePath() {
+                return directory;
+            }
+
+            @Override
+            public File getApprovedFile(String ext) {
+                return new File(directory + name + ".approved" + ext);
+            }
+
+            @Override
+            public File getReceivedFile(String ext) {
+                return new File(directory + name + ".received" + ext);
+            }
+
+            @Override
+            public ApprovalNamer addAdditionalInformation(String info) {
+                return this;
+            }
+        };
+    }
+}
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/ContractTests.java b/src/jvm/src/test/java/io/eventdriven/strictland/ContractTests.java
new file mode 100644
index 0000000..296fee1
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/ContractTests.java
@@ -0,0 +1,259 @@
+package io.eventdriven.strictland;
+
+import static java.time.ZoneOffset.UTC;
+import static java.util.Objects.requireNonNull;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import com.fasterxml.jackson.databind.DeserializationFeature;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.databind.json.JsonMapper;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import java.io.IOException;
+import java.nio.file.Path;
+import java.time.OffsetDateTime;
+import java.util.UUID;
+import org.jspecify.annotations.Nullable;
+import org.junit.jupiter.api.Test;
+
+final class ContractTests {
+    private static final UUID FIXED_CART_ID = UUID.fromString("00000000-0000-0000-0000-000000000001");
+    private static final OffsetDateTime FIXED_DATE = OffsetDateTime.of(2024, 1, 1, 12, 0, 0, 0, UTC);
+    private static final Contract CONTRACT = Contract.specification();
+    private static final ObjectMapper CUSTOM_MAPPER = new JsonMapper()
+            .registerModule(new JavaTimeModule())
+            .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
+            .configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
+
+    record ShoppingCartConfirmedV1(
+            UUID shoppingCartId, @Nullable String clientId, OffsetDateTime confirmedAt) {}
+
+    record ShoppingCartConfirmedV2(
+            UUID shoppingCartId,
+            @Nullable String clientId,
+            OffsetDateTime confirmedAt,
+            @Nullable String initializedBy) {}
+
+    record ShoppingCartConfirmed(
+            UUID shoppingCartId, @Nullable String clientId, OffsetDateTime confirmedAt) {}
+
+    record EmptyEvent() {}
+
+    record Unserializable(UUID id) {
+        @Override
+        @SuppressWarnings("DoNotCallSuggester")
+        public UUID id() {
+            throw new RuntimeException("boom");
+        }
+    }
+
+    @Test
+    void shoppingCartConfirmedV1_withCompleteData_contractIsUnchanged() {
+        CONTRACT.given(new ShoppingCartConfirmedV1(FIXED_CART_ID, "anonymised", FIXED_DATE))
+                .whenSerialized()
+                .thenContractIsUnchanged();
+    }
+
+    @Test
+    void shoppingCartConfirmedV1_withNullClientId_contractIsUnchanged() {
+        CONTRACT.given(new ShoppingCartConfirmedV1(FIXED_CART_ID, null, FIXED_DATE))
+                .whenSerialized(Snapshot.forMessageType("ShoppingCartConfirmedV1_NullClientId"))
+                .thenContractIsUnchanged();
+    }
+
+    @Test
+    void shoppingCartConfirmedV2_withRequiredData_contractIsUnchanged() {
+        CONTRACT.given(new ShoppingCartConfirmedV2(FIXED_CART_ID, "anonymised", FIXED_DATE, null))
+                .whenSerialized(Snapshot.forMessageType("ShoppingCartConfirmedV2_WithRequiredData"))
+                .thenContractIsUnchanged();
+    }
+
+    @Test
+    void shoppingCartConfirmedV2_withCompleteData_contractIsUnchanged() {
+        CONTRACT.given(new ShoppingCartConfirmedV2(FIXED_CART_ID, "anonymised", FIXED_DATE, "Oskar"))
+                .whenSerialized()
+                .thenContractIsUnchanged();
+    }
+
+    @Test
+    void givenV1Event_whenReadAsV2_thenForwardCompatible() {
+        CONTRACT.given(Snapshot.of(ShoppingCartConfirmedV1.class))
+                .whenDeserializedAs(ShoppingCartConfirmedV2.class)
+                .thenForwardCompatible(v2 -> assertNull(v2.initializedBy()));
+    }
+
+    @Test
+    void givenEvent_whenRoundTrippedAsSameType_thenForwardCompatibleWithNoExtraAssertions() {
+        CONTRACT.given(new ShoppingCartConfirmed(FIXED_CART_ID, "anonymised", FIXED_DATE))
+                .whenDeserializedAs(ShoppingCartConfirmed.class)
+                .thenForwardCompatible();
+    }
+
+    @Test
+    void givenV2Event_whenReadAsV1_thenBackwardCompatible() {
+        CONTRACT.given(new ShoppingCartConfirmedV2(FIXED_CART_ID, "anonymised", FIXED_DATE, "admin"))
+                .whenDeserializedAs(ShoppingCartConfirmedV1.class)
+                .thenBackwardCompatible();
+    }
+
+    @Test
+    void specification_withCustomMapper_isUsedForSerialization() {
+        Contract.specification(CUSTOM_MAPPER)
+                .given(new ShoppingCartConfirmed(FIXED_CART_ID, "anonymised", FIXED_DATE))
+                .whenSerialized()
+                .thenContractIsUnchanged();
+    }
+
+    @Test
+    void given_byClass_whenSerialized_verifiesAgainstSnapshotNamedAfterTheContractualType() {
+        Contract.specification()
+                .given(new ShoppingCartConfirmed(FIXED_CART_ID, "anonymised", FIXED_DATE))
+                .whenSerialized(Snapshot.of(ShoppingCartConfirmed.class))
+                .thenContractIsUnchanged();
+    }
+
+    @Test
+    void given_byMessageType_whenSerialized_verifiesAgainstNamedSnapshot() {
+        Contract.specification()
+                .given(new ShoppingCartConfirmed(FIXED_CART_ID, "anonymised", FIXED_DATE))
+                .whenSerialized(
+                        Snapshot.forMessageType("ShoppingCartConfirmed_ByMessageType", ShoppingCartConfirmed.class))
+                .thenContractIsUnchanged();
+    }
+
+    @Test
+    void given_byPath_whenSerialized_verifiesAgainstSnapshotAtPath() {
+        var path = Path.of("src/test/java/io/eventdriven/strictland/ShoppingCartConfirmed_ByPath.approved.txt");
+
+        Contract.specification()
+                .given(new ShoppingCartConfirmed(FIXED_CART_ID, "anonymised", FIXED_DATE))
+                .whenSerialized(Snapshot.at(path, ShoppingCartConfirmed.class))
+                .thenContractIsUnchanged();
+    }
+
+    @Test
+    void given_byPath_withRelativeSinglePartPath_throwsBecausePathHasNoParent() {
+        var path = Path.of("Orphan.approved.txt");
+
+        var exception = assertThrows(
+                IllegalArgumentException.class,
+                () -> Contract.specification()
+                        .given(new ShoppingCartConfirmed(FIXED_CART_ID, "anonymised", FIXED_DATE))
+                        .whenSerialized(Snapshot.at(path))
+                        .thenContractIsUnchanged());
+
+        assertTrue(requireNonNull(exception.getMessage()).contains("must have a parent directory"));
+    }
+
+    @Test
+    void given_snapshotByMessageType_whenSerialized_throwsBecauseInstanceIsRequired() {
+        var exception = assertThrows(
+                IllegalStateException.class,
+                () -> Contract.specification()
+                        .given(Snapshot.forMessageType("ShoppingCartConfirmed"))
+                        .whenSerialized());
+
+        assertTrue(requireNonNull(exception.getMessage()).contains("Contract.given(instance)"));
+    }
+
+    @Test
+    void given_snapshotByPath_whenSerialized_throwsBecauseInstanceIsRequired() {
+        var path = Path.of("src/test/java/io/eventdriven/strictland/ShoppingCartConfirmed.approved.txt");
+
+        var exception = assertThrows(
+                IllegalStateException.class,
+                () -> Contract.specification().given(Snapshot.at(path)).whenSerialized());
+
+        assertTrue(requireNonNull(exception.getMessage()).contains("Contract.given(instance)"));
+    }
+
+    @Test
+    void given_snapshotByMessageTypeWithSourceType_whenDeserializedAs_isForwardCompatible() {
+        Contract.specification()
+                .given(Snapshot.forMessageType("ShoppingCartConfirmed", ShoppingCartConfirmed.class))
+                .whenDeserializedAs(ShoppingCartConfirmed.class)
+                .thenForwardCompatible(event -> assertEquals(FIXED_CART_ID, event.shoppingCartId()));
+    }
+
+    @Test
+    void given_snapshotByPath_whenDeserializedAs_isBackwardCompatibleWithExtraAssertion() {
+        var path = Path.of("src/test/java/io/eventdriven/strictland/ShoppingCartConfirmed.approved.txt");
+
+        Contract.specification()
+                .given(Snapshot.at(path, ShoppingCartConfirmed.class))
+                .whenDeserializedAs(ShoppingCartConfirmed.class)
+                .thenBackwardCompatible(event -> assertEquals(FIXED_CART_ID, event.shoppingCartId()));
+    }
+
+    @Test
+    void given_snapshotThatDeserializesToNull_thenForwardCompatible_fails() {
+        var path = Path.of("src/test/java/io/eventdriven/strictland/Null.approved.txt");
+
+        var error = assertThrows(
+                AssertionError.class,
+                () -> Contract.specification()
+                        .given(Snapshot.at(path, ShoppingCartConfirmed.class))
+                        .whenDeserializedAs(ShoppingCartConfirmed.class)
+                        .thenForwardCompatible());
+
+        assertTrue(requireNonNull(error.getMessage()).contains("returned empty"));
+    }
+
+    @Test
+    void given_malformedSnapshot_whenDeserializedAs_wrapsDeserializationFailureInRuntimeException() {
+        var path = Path.of("src/test/java/io/eventdriven/strictland/Malformed.approved.txt");
+
+        var exception = assertThrows(
+                RuntimeException.class,
+                () -> Contract.specification()
+                        .given(Snapshot.at(path, ShoppingCartConfirmed.class))
+                        .whenDeserializedAs(ShoppingCartConfirmed.class)
+                        .thenForwardCompatible());
+
+        assertTrue(requireNonNull(exception.getMessage()).contains("Deserialization as ShoppingCartConfirmed failed"));
+        assertTrue(exception.getCause() instanceof IOException);
+    }
+
+    @Test
+    void given_missingSnapshotFile_whenDeserializedAs_wrapsFileReadFailureInRuntimeException() {
+        var path = Path.of("src/test/java/io/eventdriven/strictland/DoesNotExist.approved.txt");
+
+        var exception = assertThrows(
+                RuntimeException.class,
+                () -> Contract.specification()
+                        .given(Snapshot.at(path, ShoppingCartConfirmed.class))
+                        .whenDeserializedAs(ShoppingCartConfirmed.class)
+                        .thenForwardCompatible());
+
+        assertTrue(requireNonNull(exception.getMessage()).contains("Cannot read snapshot file"));
+        assertTrue(exception.getCause() instanceof IOException);
+    }
+
+    @Test
+    void given_unserializableInstance_whenDeserializedAs_wrapsSerializationFailureInRuntimeException() {
+        var exception = assertThrows(
+                RuntimeException.class,
+                () -> Contract.specification()
+                        .given(new Unserializable(FIXED_CART_ID))
+                        .whenDeserializedAs(EmptyEvent.class)
+                        .thenForwardCompatible());
+
+        assertTrue(requireNonNull(exception.getMessage()).contains("Serialization of Unserializable failed"));
+        assertTrue(exception.getCause() instanceof IOException);
+    }
+
+    @Test
+    void given_instanceThatDeserializesToUnserializableTarget_wrapsTargetSerializationFailure() {
+        var exception = assertThrows(
+                RuntimeException.class,
+                () -> Contract.specification()
+                        .given(new ShoppingCartConfirmed(FIXED_CART_ID, "anonymised", FIXED_DATE))
+                        .whenDeserializedAs(Unserializable.class)
+                        .thenForwardCompatible());
+
+        assertTrue(exception.getCause() instanceof IOException);
+    }
+}
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/Malformed.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/Malformed.approved.txt
new file mode 100644
index 0000000..8dc5858
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/Malformed.approved.txt
@@ -0,0 +1 @@
+{not valid json
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/Null.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/Null.approved.txt
new file mode 100644
index 0000000..ec747fa
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/Null.approved.txt
@@ -0,0 +1 @@
+null
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV1Package_hasNoPublicApiChanges.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV1Package_hasNoPublicApiChanges.approved.txt
new file mode 100644
index 0000000..6634c21
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV1Package_hasNoPublicApiChanges.approved.txt
@@ -0,0 +1,38 @@
+public interface io.eventdriven.strictland.tests.contracts.v1.ShoppingCartEvent {
+}
+
+public static final record io.eventdriven.strictland.tests.contracts.v1.ShoppingCartEvent$ProductItemAddedToShoppingCart implements io.eventdriven.strictland.tests.contracts.v1.ShoppingCartEvent {
+  public ProductItemAddedToShoppingCart(java.util.UUID, io.eventdriven.strictland.tests.contracts.v1.productitems.ProductItem);
+  public final boolean equals(java.lang.Object);
+  public final int hashCode();
+  public io.eventdriven.strictland.tests.contracts.v1.productitems.ProductItem productItem();
+  public java.util.UUID shoppingCartId();
+  public final java.lang.String toString();
+}
+
+public static final record io.eventdriven.strictland.tests.contracts.v1.ShoppingCartEvent$ShoppingCartConfirmed implements io.eventdriven.strictland.tests.contracts.v1.ShoppingCartEvent {
+  public ShoppingCartConfirmed(java.util.UUID, java.time.OffsetDateTime);
+  public java.time.OffsetDateTime confirmedAt();
+  public final boolean equals(java.lang.Object);
+  public final int hashCode();
+  public java.util.UUID shoppingCartId();
+  public final java.lang.String toString();
+}
+
+public static final record io.eventdriven.strictland.tests.contracts.v1.ShoppingCartEvent$ShoppingCartOpened implements io.eventdriven.strictland.tests.contracts.v1.ShoppingCartEvent {
+  public ShoppingCartOpened(java.util.UUID, java.util.UUID);
+  public java.util.UUID clientId();
+  public final boolean equals(java.lang.Object);
+  public final int hashCode();
+  public java.util.UUID shoppingCartId();
+  public final java.lang.String toString();
+}
+
+public final record io.eventdriven.strictland.tests.contracts.v1.productitems.ProductItem {
+  public ProductItem(java.util.UUID, int);
+  public final boolean equals(java.lang.Object);
+  public final int hashCode();
+  public java.util.UUID productId();
+  public int quantity();
+  public final java.lang.String toString();
+}
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_excludingComparisonMethod_hidesItFromTheSurface.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_excludingComparisonMethod_hidesItFromTheSurface.approved.txt
new file mode 100644
index 0000000..ae00183
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_excludingComparisonMethod_hidesItFromTheSurface.approved.txt
@@ -0,0 +1,16 @@
+public enum io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus {
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.CANCELLED;
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.CONFIRMED;
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.PENDING;
+  public static io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus valueOf(java.lang.String);
+  public static io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus[] values();
+}
+
+public class io.eventdriven.strictland.tests.contracts.v2.ShoppingCartSummary implements java.lang.Comparable {
+  public final java.util.UUID io.eventdriven.strictland.tests.contracts.v2.ShoppingCartSummary.shoppingCartId;
+  public ShoppingCartSummary(java.util.UUID, io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus);
+  public boolean equals(java.lang.Object);
+  public io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus getStatus();
+  public int hashCode();
+  public java.lang.String toString();
+}
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_excludingConstructors_focusesOnFieldsAndMethods.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_excludingConstructors_focusesOnFieldsAndMethods.approved.txt
new file mode 100644
index 0000000..d726995
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_excludingConstructors_focusesOnFieldsAndMethods.approved.txt
@@ -0,0 +1,16 @@
+public enum io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus {
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.CANCELLED;
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.CONFIRMED;
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.PENDING;
+  public static io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus valueOf(java.lang.String);
+  public static io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus[] values();
+}
+
+public class io.eventdriven.strictland.tests.contracts.v2.ShoppingCartSummary implements java.lang.Comparable {
+  public final java.util.UUID io.eventdriven.strictland.tests.contracts.v2.ShoppingCartSummary.shoppingCartId;
+  public int compareTo(io.eventdriven.strictland.tests.contracts.v2.ShoppingCartSummary);
+  public boolean equals(java.lang.Object);
+  public io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus getStatus();
+  public int hashCode();
+  public java.lang.String toString();
+}
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_excludingStandardObjectMethods_hidesEqualsHashCodeAndToString.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_excludingStandardObjectMethods_hidesEqualsHashCodeAndToString.approved.txt
new file mode 100644
index 0000000..68cbb7c
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_excludingStandardObjectMethods_hidesEqualsHashCodeAndToString.approved.txt
@@ -0,0 +1,14 @@
+public enum io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus {
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.CANCELLED;
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.CONFIRMED;
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.PENDING;
+  public static io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus valueOf(java.lang.String);
+  public static io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus[] values();
+}
+
+public class io.eventdriven.strictland.tests.contracts.v2.ShoppingCartSummary implements java.lang.Comparable {
+  public final java.util.UUID io.eventdriven.strictland.tests.contracts.v2.ShoppingCartSummary.shoppingCartId;
+  public ShoppingCartSummary(java.util.UUID, io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus);
+  public int compareTo(io.eventdriven.strictland.tests.contracts.v2.ShoppingCartSummary);
+  public io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus getStatus();
+}
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_hasNoPublicApiChanges.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_hasNoPublicApiChanges.approved.txt
new file mode 100644
index 0000000..e5ee4c2
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_hasNoPublicApiChanges.approved.txt
@@ -0,0 +1,17 @@
+public enum io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus {
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.CANCELLED;
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.CONFIRMED;
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.PENDING;
+  public static io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus valueOf(java.lang.String);
+  public static io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus[] values();
+}
+
+public class io.eventdriven.strictland.tests.contracts.v2.ShoppingCartSummary implements java.lang.Comparable {
+  public final java.util.UUID io.eventdriven.strictland.tests.contracts.v2.ShoppingCartSummary.shoppingCartId;
+  public ShoppingCartSummary(java.util.UUID, io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus);
+  public int compareTo(io.eventdriven.strictland.tests.contracts.v2.ShoppingCartSummary);
+  public boolean equals(java.lang.Object);
+  public io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus getStatus();
+  public int hashCode();
+  public java.lang.String toString();
+}
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_onlyGettersAndFields_summarisesObservableState.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_onlyGettersAndFields_summarisesObservableState.approved.txt
new file mode 100644
index 0000000..3ddc683
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.contractsV2Package_onlyGettersAndFields_summarisesObservableState.approved.txt
@@ -0,0 +1,11 @@
+public enum io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus {
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.CANCELLED;
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.CONFIRMED;
+  public static final io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus.PENDING;
+  public static io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus[] values();
+}
+
+public class io.eventdriven.strictland.tests.contracts.v2.ShoppingCartSummary implements java.lang.Comparable {
+  public final java.util.UUID io.eventdriven.strictland.tests.contracts.v2.ShoppingCartSummary.shoppingCartId;
+  public io.eventdriven.strictland.tests.contracts.v2.ShoppingCartStatus getStatus();
+}
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.java b/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.java
new file mode 100644
index 0000000..138359d
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/PublicApiScannerExampleTests.java
@@ -0,0 +1,59 @@
+package io.eventdriven.strictland;
+
+import org.approvaltests.Approvals;
+import org.junit.jupiter.api.Test;
+
+final class PublicApiScannerExampleTests {
+
+    @Test
+    void contractsV1Package_hasNoPublicApiChanges() {
+        var api = PublicApiScanner.forPackage("io.eventdriven.strictland.tests.contracts.v1")
+                .generate();
+
+        Approvals.verify(api);
+    }
+
+    @Test
+    void contractsV2Package_hasNoPublicApiChanges() {
+        var api = PublicApiScanner.forPackage("io.eventdriven.strictland.tests.contracts.v2")
+                .generate();
+
+        Approvals.verify(api);
+    }
+
+    @Test
+    void contractsV2Package_excludingComparisonMethod_hidesItFromTheSurface() {
+        var api = PublicApiScanner.forPackage("io.eventdriven.strictland.tests.contracts.v2")
+                .excludingMethods(m -> m.getName().equals("compareTo"))
+                .generate();
+
+        Approvals.verify(api);
+    }
+
+    @Test
+    void contractsV2Package_excludingConstructors_focusesOnFieldsAndMethods() {
+        var api = PublicApiScanner.forPackage("io.eventdriven.strictland.tests.contracts.v2")
+                .excludeConstructors()
+                .generate();
+
+        Approvals.verify(api);
+    }
+
+    @Test
+    void contractsV2Package_excludingStandardObjectMethods_hidesEqualsHashCodeAndToString() {
+        var api = PublicApiScanner.forPackage("io.eventdriven.strictland.tests.contracts.v2")
+                .excludeStandardObjectMethods()
+                .generate();
+
+        Approvals.verify(api);
+    }
+
+    @Test
+    void contractsV2Package_onlyGettersAndFields_summarisesObservableState() {
+        var api = PublicApiScanner.forPackage("io.eventdriven.strictland.tests.contracts.v2")
+                .onlyGettersAndFields()
+                .generate();
+
+        Approvals.verify(api);
+    }
+}
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmed.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmed.approved.txt
new file mode 100644
index 0000000..d3cd1f2
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmed.approved.txt
@@ -0,0 +1 @@
+{"shoppingCartId":"00000000-0000-0000-0000-000000000001","clientId":"anonymised","confirmedAt":"2024-01-01T12:00:00Z"}
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmedV1.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmedV1.approved.txt
new file mode 100644
index 0000000..d3cd1f2
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmedV1.approved.txt
@@ -0,0 +1 @@
+{"shoppingCartId":"00000000-0000-0000-0000-000000000001","clientId":"anonymised","confirmedAt":"2024-01-01T12:00:00Z"}
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmedV1_NullClientId.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmedV1_NullClientId.approved.txt
new file mode 100644
index 0000000..3ec47fe
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmedV1_NullClientId.approved.txt
@@ -0,0 +1 @@
+{"shoppingCartId":"00000000-0000-0000-0000-000000000001","clientId":null,"confirmedAt":"2024-01-01T12:00:00Z"}
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmedV2.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmedV2.approved.txt
new file mode 100644
index 0000000..1854076
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmedV2.approved.txt
@@ -0,0 +1 @@
+{"shoppingCartId":"00000000-0000-0000-0000-000000000001","clientId":"anonymised","confirmedAt":"2024-01-01T12:00:00Z","initializedBy":"Oskar"}
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmedV2_WithRequiredData.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmedV2_WithRequiredData.approved.txt
new file mode 100644
index 0000000..bcb355f
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmedV2_WithRequiredData.approved.txt
@@ -0,0 +1 @@
+{"shoppingCartId":"00000000-0000-0000-0000-000000000001","clientId":"anonymised","confirmedAt":"2024-01-01T12:00:00Z","initializedBy":null}
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmed_ByMessageType.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmed_ByMessageType.approved.txt
new file mode 100644
index 0000000..d3cd1f2
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmed_ByMessageType.approved.txt
@@ -0,0 +1 @@
+{"shoppingCartId":"00000000-0000-0000-0000-000000000001","clientId":"anonymised","confirmedAt":"2024-01-01T12:00:00Z"}
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmed_ByPath.approved.txt b/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmed_ByPath.approved.txt
new file mode 100644
index 0000000..d3cd1f2
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/ShoppingCartConfirmed_ByPath.approved.txt
@@ -0,0 +1 @@
+{"shoppingCartId":"00000000-0000-0000-0000-000000000001","clientId":"anonymised","confirmedAt":"2024-01-01T12:00:00Z"}
\ No newline at end of file
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v1/ShoppingCartEvent.java b/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v1/ShoppingCartEvent.java
new file mode 100644
index 0000000..d242174
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v1/ShoppingCartEvent.java
@@ -0,0 +1,14 @@
+package io.eventdriven.strictland.tests.contracts.v1;
+
+import io.eventdriven.strictland.tests.contracts.v1.productitems.ProductItem;
+import java.time.OffsetDateTime;
+import java.util.UUID;
+
+public sealed interface ShoppingCartEvent {
+
+    record ShoppingCartOpened(UUID shoppingCartId, UUID clientId) implements ShoppingCartEvent {}
+
+    record ProductItemAddedToShoppingCart(UUID shoppingCartId, ProductItem productItem) implements ShoppingCartEvent {}
+
+    record ShoppingCartConfirmed(UUID shoppingCartId, OffsetDateTime confirmedAt) implements ShoppingCartEvent {}
+}
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v1/package-info.java b/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v1/package-info.java
new file mode 100644
index 0000000..0211da1
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v1/package-info.java
@@ -0,0 +1,4 @@
+@NullMarked
+package io.eventdriven.strictland.tests.contracts.v1;
+
+import org.jspecify.annotations.NullMarked;
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v1/productitems/ProductItem.java b/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v1/productitems/ProductItem.java
new file mode 100644
index 0000000..db7c8e1
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v1/productitems/ProductItem.java
@@ -0,0 +1,5 @@
+package io.eventdriven.strictland.tests.contracts.v1.productitems;
+
+import java.util.UUID;
+
+public record ProductItem(UUID productId, int quantity) {}
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v1/productitems/package-info.java b/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v1/productitems/package-info.java
new file mode 100644
index 0000000..e2c0455
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v1/productitems/package-info.java
@@ -0,0 +1,4 @@
+@NullMarked
+package io.eventdriven.strictland.tests.contracts.v1.productitems;
+
+import org.jspecify.annotations.NullMarked;
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v2/ShoppingCartStatus.java b/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v2/ShoppingCartStatus.java
new file mode 100644
index 0000000..b890ba8
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v2/ShoppingCartStatus.java
@@ -0,0 +1,7 @@
+package io.eventdriven.strictland.tests.contracts.v2;
+
+public enum ShoppingCartStatus {
+    PENDING,
+    CONFIRMED,
+    CANCELLED
+}
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v2/ShoppingCartSummary.java b/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v2/ShoppingCartSummary.java
new file mode 100644
index 0000000..6a6a7b8
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v2/ShoppingCartSummary.java
@@ -0,0 +1,40 @@
+package io.eventdriven.strictland.tests.contracts.v2;
+
+import java.util.Objects;
+import java.util.UUID;
+
+public class ShoppingCartSummary implements Comparable<ShoppingCartSummary> {
+    public final UUID shoppingCartId;
+    private final ShoppingCartStatus status;
+
+    public ShoppingCartSummary(UUID shoppingCartId, ShoppingCartStatus status) {
+        this.shoppingCartId = shoppingCartId;
+        this.status = status;
+    }
+
+    public ShoppingCartStatus getStatus() {
+        return status;
+    }
+
+    @Override
+    public int compareTo(ShoppingCartSummary other) {
+        return shoppingCartId.compareTo(other.shoppingCartId);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof ShoppingCartSummary other)) return false;
+        return shoppingCartId.equals(other.shoppingCartId) && status == other.status;
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(shoppingCartId, status);
+    }
+
+    @Override
+    public String toString() {
+        return "ShoppingCartSummary{shoppingCartId=" + shoppingCartId + ", status=" + status + "}";
+    }
+}
diff --git a/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v2/package-info.java b/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v2/package-info.java
new file mode 100644
index 0000000..8657708
--- /dev/null
+++ b/src/jvm/src/test/java/io/eventdriven/strictland/tests/contracts/v2/package-info.java
@@ -0,0 +1,4 @@
+@NullMarked
+package io.eventdriven.strictland.tests.contracts.v2;
+
+import org.jspecify.annotations.NullMarked;