diff --git a/Cargo.lock b/Cargo.lock
index 06c12a9e0757f..c81da77116ed5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1745,6 +1745,7 @@ dependencies = [
  "criterion",
  "ctor",
  "dashmap",
+ "datafusion",
  "datafusion-catalog",
  "datafusion-catalog-listing",
  "datafusion-common",
@@ -1927,6 +1928,7 @@ dependencies = [
  "arrow-schema",
  "chrono",
  "criterion",
+ "datafusion-common",
  "foldhash 0.2.0",
  "half",
  "hashbrown 0.17.1",
@@ -1969,6 +1971,7 @@ dependencies = [
  "criterion",
  "datafusion-common",
  "datafusion-common-runtime",
+ "datafusion-datasource",
  "datafusion-execution",
  "datafusion-expr",
  "datafusion-functions",
@@ -2206,6 +2209,7 @@ dependencies = [
  "ctor",
  "datafusion-common",
  "datafusion-doc",
+ "datafusion-expr",
  "datafusion-expr-common",
  "datafusion-functions-aggregate-common",
  "datafusion-functions-window-common",
@@ -2545,6 +2549,7 @@ dependencies = [
  "datafusion-functions-window-common",
  "datafusion-physical-expr",
  "datafusion-physical-expr-common",
+ "datafusion-physical-plan",
  "datafusion-proto-common",
  "datafusion-proto-models",
  "futures",
diff --git a/datafusion-cli/Cargo.toml b/datafusion-cli/Cargo.toml
index aa508123d6e05..4e3ec4e0143b0 100644
--- a/datafusion-cli/Cargo.toml
+++ b/datafusion-cli/Cargo.toml
@@ -75,6 +75,7 @@ workspace = true
 
 [dev-dependencies]
 ctor = { workspace = true }
+datafusion-common = { workspace = true, features = ["test_utils"] }
 insta = { workspace = true }
 insta-cmd = "0.7.0"
 rstest = { workspace = true }
diff --git a/datafusion-examples/Cargo.toml b/datafusion-examples/Cargo.toml
index 6d6d917ac46ec..84ebe0f6f5c44 100644
--- a/datafusion-examples/Cargo.toml
+++ b/datafusion-examples/Cargo.toml
@@ -51,6 +51,8 @@ bytes = { workspace = true }
 dashmap = { workspace = true }
 # note only use main datafusion crate for examples
 base64 = "0.23.0"
+datafusion = { workspace = true, features = ["test_utils"] }
+datafusion-common = { workspace = true, features = ["test_utils"] }
 datafusion-expr = { workspace = true }
 datafusion-physical-expr-adapter = { workspace = true }
 datafusion-proto = { workspace = true, features = ["parquet"] }
diff --git a/datafusion/catalog/Cargo.toml b/datafusion/catalog/Cargo.toml
index 1009e9aee477b..e95abf6db518b 100644
--- a/datafusion/catalog/Cargo.toml
+++ b/datafusion/catalog/Cargo.toml
@@ -30,6 +30,10 @@ version.workspace = true
 [package.metadata.docs.rs]
 all-features = true
 
+[features]
+# Exposes internal test utilities for use by other DataFusion crates.
+test_utils = []
+
 [dependencies]
 arrow = { workspace = true }
 async-trait = { workspace = true }
diff --git a/datafusion/catalog/src/memory/table.rs b/datafusion/catalog/src/memory/table.rs
index 9cfa32e0d09fe..4d1413f5fc6c4 100644
--- a/datafusion/catalog/src/memory/table.rs
+++ b/datafusion/catalog/src/memory/table.rs
@@ -71,8 +71,17 @@ pub use datafusion_datasource::memory::PartitionData;
 #[derive(Debug)]
 pub struct MemTable {
     schema: SchemaRef,
-    // batches used to be pub(crate), but it's needed to be public for the tests
+    /// # Public Only for Internal Use:
+    /// Batches exposed for the memory table tests in `datafusion`. Not part of the
+    /// supported public API.
+    /// See the [API health policy] for details.
+    ///
+    /// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+    #[cfg(any(test, feature = "test_utils"))]
+    #[doc(hidden)]
     pub batches: Vec<PartitionData>,
+    #[cfg(not(any(test, feature = "test_utils")))]
+    batches: Vec<PartitionData>,
     constraints: Constraints,
     column_defaults: HashMap<String, Expr>,
     /// Optional pre-known sort order(s). Must be `SortExpr`s.
diff --git a/datafusion/common/Cargo.toml b/datafusion/common/Cargo.toml
index 9ee199fe82f28..63f5402a3c2f0 100644
--- a/datafusion/common/Cargo.toml
+++ b/datafusion/common/Cargo.toml
@@ -41,6 +41,8 @@ workspace = true
 name = "datafusion_common"
 
 [features]
+# Exposes internal test utilities for use by other DataFusion crates.
+test_utils = []
 backtrace = []
 parquet_encryption = [
     "parquet",
@@ -95,6 +97,7 @@ web-time = "1.1.0"
 [dev-dependencies]
 chrono = { workspace = true }
 criterion = { workspace = true }
+datafusion-common = { workspace = true, features = ["test_utils"] }
 insta = { workspace = true }
 rand = { workspace = true }
 sqlparser = { workspace = true }
diff --git a/datafusion/common/src/lib.rs b/datafusion/common/src/lib.rs
index 2eebfe4963057..127eb60137741 100644
--- a/datafusion/common/src/lib.rs
+++ b/datafusion/common/src/lib.rs
@@ -60,6 +60,13 @@ pub mod rounding;
 pub mod scalar;
 pub mod spans;
 pub mod stats;
+/// # Public Only for Internal Use:
+/// Shared test helpers for DataFusion crates. Not part of the supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+#[cfg(any(test, feature = "test_utils"))]
+#[doc(hidden)]
 pub mod test_util;
 pub mod tree_node;
 pub mod types;
diff --git a/datafusion/common/src/test_util.rs b/datafusion/common/src/test_util.rs
index 348fe2ef547f0..89dad5f67d441 100644
--- a/datafusion/common/src/test_util.rs
+++ b/datafusion/common/src/test_util.rs
@@ -68,7 +68,14 @@ pub fn format_batches(results: &[RecordBatch]) -> Result<impl Display, ArrowErro
 /// // compare the formatted output of the record batch with the expected output
 /// assert_batches_eq!(expected, &[batch]);
 /// ```
+///
+/// # Public Only for Internal Use:
+/// Shared test assertions for DataFusion crates. Not part of the supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
 #[macro_export]
+#[doc(hidden)]
 macro_rules! assert_batches_eq {
     ($EXPECTED_LINES: expr, $CHUNKS: expr) => {
         let expected_lines: Vec<String> =
@@ -117,7 +124,14 @@ pub fn batches_to_sort_string(batches: &[RecordBatch]) -> String {
 /// Expects to be called about like this:
 ///
 /// `assert_batch_sorted_eq!(expected_lines: &[&str], batches: &[RecordBatch])`
+///
+/// # Public Only for Internal Use:
+/// Shared test assertions for DataFusion crates. Not part of the supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
 #[macro_export]
+#[doc(hidden)]
 macro_rules! assert_batches_sorted_eq {
     ($EXPECTED_LINES: expr, $CHUNKS: expr) => {
         let mut expected_lines: Vec<String> =
@@ -159,7 +173,14 @@ macro_rules! assert_batches_sorted_eq {
 /// messages are on the same line as the failure;
 ///
 /// Both arguments must be convertible into Strings ([`Into`]<[`String`]>)
+///
+/// # Public Only for Internal Use:
+/// Shared test assertions for DataFusion crates. Not part of the supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
 #[macro_export]
+#[doc(hidden)]
 macro_rules! assert_contains {
     ($ACTUAL: expr, $EXPECTED: expr) => {
         let actual_value: String = $ACTUAL.into();
@@ -182,7 +203,14 @@ macro_rules! assert_contains {
 /// messages are on the same line as the failure;
 ///
 /// Both arguments must be convertible into Strings ([`Into`]<[`String`]>)
+///
+/// # Public Only for Internal Use:
+/// Shared test assertions for DataFusion crates. Not part of the supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
 #[macro_export]
+#[doc(hidden)]
 macro_rules! assert_not_contains {
     ($ACTUAL: expr, $UNEXPECTED: expr) => {
         let actual_value: String = $ACTUAL.into();
@@ -318,7 +346,14 @@ pub fn get_data_dir(
     }
 }
 
+/// # Public Only for Internal Use:
+/// Array construction for test macros in DataFusion crates. Not part of the supported
+/// public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
 #[macro_export]
+#[doc(hidden)]
 macro_rules! create_array {
     (Boolean, $values: expr) => {
         std::sync::Arc::new($crate::arrow::array::BooleanArray::from($values))
@@ -377,8 +412,16 @@ macro_rules! create_array {
 ///     ("c", Utf8, vec!["alpha", "beta", "gamma"])
 /// );
 /// ```
+///
+/// # Public Only for Internal Use:
+/// Record batch construction for tests in DataFusion crates. Not part of the supported
+/// public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
 #[deprecated(since = "55.0.0", note = "Use `arrow::array::record_batch` instead")]
 #[macro_export]
+#[doc(hidden)]
 macro_rules! record_batch {
     ($(($name: expr, $type: ident, $values: expr)),*) => {
         {
diff --git a/datafusion/core/Cargo.toml b/datafusion/core/Cargo.toml
index 222c0ec688b78..7eb7f0020cc99 100644
--- a/datafusion/core/Cargo.toml
+++ b/datafusion/core/Cargo.toml
@@ -39,6 +39,15 @@ all-features = true
 workspace = true
 
 [features]
+# Exposes internal test utilities for use by other DataFusion crates.
+test_utils = [
+    "datafusion-catalog/test_utils",
+    "datafusion-common/test_utils",
+    "datafusion-datasource/test_utils",
+    "datafusion-expr/test_utils",
+    "datafusion-physical-expr/test_utils",
+    "datafusion-physical-plan/test_utils",
+]
 # Enables the `print_config_docs`, `print_runtime_config_docs` and
 # `print_functions_docs` binaries, which regenerate the docs under
 # `docs/source/user-guide`. Off by default: they are only run by
@@ -171,6 +180,7 @@ async-trait = { workspace = true }
 criterion = { workspace = true, features = ["async_tokio", "async_futures"] }
 ctor = { workspace = true }
 dashmap = "6.2.1"
+datafusion = { workspace = true, features = ["test_utils"] }
 datafusion-doc = { workspace = true }
 datafusion-functions-window-common = { workspace = true }
 datafusion-macros = { workspace = true }
diff --git a/datafusion/core/src/lib.rs b/datafusion/core/src/lib.rs
index 28ea4b4490c3e..78c084ce482c1 100644
--- a/datafusion/core/src/lib.rs
+++ b/datafusion/core/src/lib.rs
@@ -854,8 +854,23 @@ pub mod physical_plan {
     pub use datafusion_physical_plan::*;
 }
 
-// Reexport testing macros for compatibility
+/// # Public Only for Internal Use:
+/// Test assertions re-exported for compatibility across DataFusion crates. Not part of
+/// the supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+#[cfg(any(test, feature = "test_utils"))]
+#[doc(hidden)]
 pub use datafusion_common::assert_batches_eq;
+/// # Public Only for Internal Use:
+/// Test assertions re-exported for compatibility across DataFusion crates. Not part of
+/// the supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+#[cfg(any(test, feature = "test_utils"))]
+#[doc(hidden)]
 pub use datafusion_common::assert_batches_sorted_eq;
 
 /// re-export of [`datafusion_sql`] crate
@@ -895,10 +910,24 @@ pub mod variable {
     pub use datafusion_expr::var_provider::{VarProvider, VarType};
 }
 
+/// # Public Only for Internal Use:
+/// Shared test helpers for DataFusion crates. Not part of the supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
 #[cfg(not(target_arch = "wasm32"))]
+#[cfg(any(test, feature = "test_utils"))]
+#[doc(hidden)]
 pub mod test;
 
 mod schema_equivalence;
+/// # Public Only for Internal Use:
+/// Shared test helpers for DataFusion crates. Not part of the supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+#[cfg(any(test, feature = "test_utils"))]
+#[doc(hidden)]
 pub mod test_util;
 
 #[cfg(doctest)]
diff --git a/datafusion/datasource-avro/Cargo.toml b/datafusion/datasource-avro/Cargo.toml
index 63e949e21def9..671de1d77df90 100644
--- a/datafusion/datasource-avro/Cargo.toml
+++ b/datafusion/datasource-avro/Cargo.toml
@@ -59,6 +59,7 @@ object_store = { workspace = true }
 tokio = { workspace = true }
 
 [dev-dependencies]
+datafusion-common = { workspace = true, features = ["test_utils"] }
 
 # Note: add additional linter rules in lib.rs.
 # Rust does not support workspace + new linter rules in subcrates yet
diff --git a/datafusion/datasource-parquet/Cargo.toml b/datafusion/datasource-parquet/Cargo.toml
index a2589af19a6ee..be0e404b07705 100644
--- a/datafusion/datasource-parquet/Cargo.toml
+++ b/datafusion/datasource-parquet/Cargo.toml
@@ -60,6 +60,7 @@ tokio = { workspace = true }
 [dev-dependencies]
 chrono = { workspace = true }
 criterion = { workspace = true }
+datafusion-common = { workspace = true, features = ["test_utils"] }
 datafusion-functions = { workspace = true }
 datafusion-functions-nested = { workspace = true }
 tempfile = { workspace = true }
diff --git a/datafusion/datasource/Cargo.toml b/datafusion/datasource/Cargo.toml
index f09447b694f52..d06a42093a1d8 100644
--- a/datafusion/datasource/Cargo.toml
+++ b/datafusion/datasource/Cargo.toml
@@ -31,6 +31,8 @@ version.workspace = true
 all-features = true
 
 [features]
+# Exposes internal test utilities for use by other DataFusion crates.
+test_utils = []
 backtrace = ["datafusion-common/backtrace"]
 compression = ["async-compression", "liblzma", "bzip2", "flate2", "zstd", "tokio-util"]
 default = ["compression"]
@@ -83,6 +85,8 @@ zstd = { workspace = true, optional = true }
 
 [dev-dependencies]
 criterion = { workspace = true }
+datafusion-common = { workspace = true, features = ["test_utils"] }
+datafusion-datasource = { workspace = true, features = ["test_utils"] }
 datafusion-functions = { workspace = true }
 insta = { workspace = true }
 tempfile = { workspace = true }
diff --git a/datafusion/datasource/src/mod.rs b/datafusion/datasource/src/mod.rs
index d0bf64d81c71f..df5951d4d4909 100644
--- a/datafusion/datasource/src/mod.rs
+++ b/datafusion/datasource/src/mod.rs
@@ -58,10 +58,13 @@ pub mod url;
 pub mod write;
 pub use self::file::as_file_source;
 pub use self::url::ListingTableUrl;
+#[cfg(any(test, feature = "test_utils"))]
 use crate::file_groups::FileGroup;
 use arrow::datatypes::SchemaRef;
 use chrono::TimeZone;
-use datafusion_common::stats::{Precision, is_known_empty};
+use datafusion_common::stats::Precision;
+#[cfg(any(test, feature = "test_utils"))]
+use datafusion_common::stats::is_known_empty;
 use datafusion_common::{ColumnStatistics, Result, TableReference};
 use datafusion_common::{ScalarValue, Statistics};
 use datafusion_physical_expr::LexOrdering;
@@ -450,6 +453,14 @@ impl From<ObjectMeta> for PartitionedFile {
 /// File 2: [40, 140]
 /// File 3: [60, 160]
 /// File 4: [80, 180]
+///
+/// # Public Only for Internal Use:
+/// Used by file group tests and benchmarks. Not part of the supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+#[cfg(any(test, feature = "test_utils"))]
+#[doc(hidden)]
 pub fn generate_test_files(num_files: usize, overlap_factor: f64) -> Vec<FileGroup> {
     let mut files = Vec::with_capacity(num_files);
     if num_files == 0 {
@@ -500,8 +511,15 @@ pub fn generate_test_files(num_files: usize, overlap_factor: f64) -> Vec<FileGro
     vec![FileGroup::new(files)]
 }
 
-// Helper function to verify that files within each group maintain sort order
-/// Used by tests and benchmarks
+/// Verifies that files within each group maintain sort order.
+///
+/// # Public Only for Internal Use:
+/// Used by file group tests and benchmarks. Not part of the supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+#[cfg(any(test, feature = "test_utils"))]
+#[doc(hidden)]
 pub fn verify_sort_integrity(file_groups: &[FileGroup]) -> bool {
     for group in file_groups {
         // Known-empty files contribute no rows and may not have min/max
diff --git a/datafusion/expr-common/Cargo.toml b/datafusion/expr-common/Cargo.toml
index 026c1e0bc316b..acb439b372935 100644
--- a/datafusion/expr-common/Cargo.toml
+++ b/datafusion/expr-common/Cargo.toml
@@ -47,5 +47,6 @@ indexmap = { workspace = true }
 itertools = { workspace = true }
 
 [dev-dependencies]
+datafusion-common = { workspace = true, features = ["test_utils"] }
 insta = { workspace = true }
 rstest = { workspace = true }
diff --git a/datafusion/expr/Cargo.toml b/datafusion/expr/Cargo.toml
index 74b85501dde91..5c9e5cf426211 100644
--- a/datafusion/expr/Cargo.toml
+++ b/datafusion/expr/Cargo.toml
@@ -41,6 +41,8 @@ workspace = true
 name = "datafusion_expr"
 
 [features]
+# Exposes internal test utilities for use by other DataFusion crates.
+test_utils = []
 default = ["sql"]
 # Enables protobuf conversions for the expression types owned by this crate.
 # Off by default so consumers that never serialize plans pay nothing. Mirrors
@@ -71,6 +73,8 @@ sqlparser = { workspace = true, optional = true }
 [dev-dependencies]
 criterion = { workspace = true }
 ctor = { workspace = true }
+datafusion-common = { workspace = true, features = ["test_utils"] }
+datafusion-expr = { workspace = true, features = ["test_utils"] }
 env_logger = { workspace = true }
 insta = { workspace = true }
 # Makes sure `test_display_pg_json` behaves in a consistent way regardless of
diff --git a/datafusion/expr/src/lib.rs b/datafusion/expr/src/lib.rs
index ed9b4df4ce2bd..cffd3bb230b5b 100644
--- a/datafusion/expr/src/lib.rs
+++ b/datafusion/expr/src/lib.rs
@@ -88,6 +88,14 @@ pub mod preimage;
 pub mod ptr_eq;
 #[cfg(not(feature = "sql"))]
 pub mod sql;
+/// # Public Only for Internal Use:
+/// Function stubs shared by tests in DataFusion crates. Not part of the supported
+/// public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+#[cfg(any(test, feature = "test_utils"))]
+#[doc(hidden)]
 pub mod test;
 pub mod tree_node;
 pub mod type_coercion;
diff --git a/datafusion/ffi/Cargo.toml b/datafusion/ffi/Cargo.toml
index affcff3dbdcd9..9e9dcbe9e54d0 100644
--- a/datafusion/ffi/Cargo.toml
+++ b/datafusion/ffi/Cargo.toml
@@ -75,7 +75,8 @@ stabby = "72.1.2"
 tokio = { workspace = true }
 
 [dev-dependencies]
-datafusion = { workspace = true, default-features = false, features = ["sql"] }
+datafusion = { workspace = true, default-features = false, features = ["test_utils", "sql"] }
+datafusion-common = { workspace = true, features = ["test_utils"] }
 datafusion-functions = { workspace = true }
 datafusion-functions-aggregate = { workspace = true }
 datafusion-functions-aggregate-common = { workspace = true }
diff --git a/datafusion/functions-aggregate-common/Cargo.toml b/datafusion/functions-aggregate-common/Cargo.toml
index 463034d4d6de3..977952845400f 100644
--- a/datafusion/functions-aggregate-common/Cargo.toml
+++ b/datafusion/functions-aggregate-common/Cargo.toml
@@ -41,6 +41,8 @@ workspace = true
 name = "datafusion_functions_aggregate_common"
 
 [features]
+# Exposes internal test utilities for use by other DataFusion crates.
+test_utils = []
 # Used for testing ONLY: causes all values to hash to the same value (test for collisions)
 force_hash_collisions = ["datafusion-common/force_hash_collisions"]
 
diff --git a/datafusion/functions-aggregate-common/src/tdigest.rs b/datafusion/functions-aggregate-common/src/tdigest.rs
index 860f56f6c00dc..6adb2e9d92dd8 100644
--- a/datafusion/functions-aggregate-common/src/tdigest.rs
+++ b/datafusion/functions-aggregate-common/src/tdigest.rs
@@ -206,7 +206,16 @@ impl TDigest {
         v.clamp(min, max)
     }
 
-    // public for testing in other modules
+    /// Merge unsorted values.
+    ///
+    /// # Public Only for Internal Use:
+    /// Used by tests in `datafusion-functions-aggregate`. Not part of the supported
+    /// public API.
+    /// See the [API health policy] for details.
+    ///
+    /// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+    #[cfg(any(test, feature = "test_utils"))]
+    #[doc(hidden)]
     pub fn merge_unsorted_f64(&self, unsorted_values: Vec<f64>) -> TDigest {
         let mut values = unsorted_values;
         values.sort_by(|a, b| a.total_cmp(b));
diff --git a/datafusion/functions-aggregate/Cargo.toml b/datafusion/functions-aggregate/Cargo.toml
index ead59720d216e..05145dcb3928d 100644
--- a/datafusion/functions-aggregate/Cargo.toml
+++ b/datafusion/functions-aggregate/Cargo.toml
@@ -60,6 +60,7 @@ num-traits = { workspace = true }
 [dev-dependencies]
 arrow = { workspace = true, features = ["test_utils"] }
 criterion = { workspace = true }
+datafusion-functions-aggregate-common = { workspace = true, features = ["test_utils"] }
 rand = { workspace = true }
 
 [[bench]]
diff --git a/datafusion/functions-nested/Cargo.toml b/datafusion/functions-nested/Cargo.toml
index 728255cecf252..745e27b4bb39d 100644
--- a/datafusion/functions-nested/Cargo.toml
+++ b/datafusion/functions-nested/Cargo.toml
@@ -66,6 +66,7 @@ memchr = { workspace = true }
 [dev-dependencies]
 arrow = { workspace = true, features = ["test_utils"] }
 criterion = { workspace = true, features = ["async_tokio"] }
+datafusion-common = { workspace = true, features = ["test_utils"] }
 rand = { workspace = true }
 # used to test array_transform
 datafusion-physical-expr = { workspace = true }
diff --git a/datafusion/functions/Cargo.toml b/datafusion/functions/Cargo.toml
index 28765bdda9e2e..5e9cea6a61ed5 100644
--- a/datafusion/functions/Cargo.toml
+++ b/datafusion/functions/Cargo.toml
@@ -94,6 +94,7 @@ uuid = { workspace = true, features = ["v4"], optional = true }
 arrow = { workspace = true, features = ["test_utils"] }
 criterion = { workspace = true }
 ctor = { workspace = true }
+datafusion-common = { workspace = true, features = ["test_utils"] }
 env_logger = { workspace = true }
 rand = { workspace = true }
 tokio = { workspace = true, features = ["macros", "rt", "sync"] }
diff --git a/datafusion/optimizer/Cargo.toml b/datafusion/optimizer/Cargo.toml
index 31a73062e119e..49d9a7f116411 100644
--- a/datafusion/optimizer/Cargo.toml
+++ b/datafusion/optimizer/Cargo.toml
@@ -69,6 +69,8 @@ regex-syntax = "0.8.9"
 async-trait = { workspace = true }
 criterion = { workspace = true }
 ctor = { workspace = true }
+datafusion-common = { workspace = true, features = ["test_utils"] }
+datafusion-expr = { workspace = true, features = ["test_utils"] }
 datafusion-functions-aggregate = { workspace = true }
 datafusion-functions-window = { workspace = true }
 datafusion-functions-window-common = { workspace = true }
diff --git a/datafusion/physical-expr-adapter/Cargo.toml b/datafusion/physical-expr-adapter/Cargo.toml
index 453c8bdaacb4a..af97f87def834 100644
--- a/datafusion/physical-expr-adapter/Cargo.toml
+++ b/datafusion/physical-expr-adapter/Cargo.toml
@@ -28,3 +28,4 @@ itertools = { workspace = true }
 workspace = true
 
 [dev-dependencies]
+datafusion-common = { workspace = true, features = ["test_utils"] }
diff --git a/datafusion/physical-expr/Cargo.toml b/datafusion/physical-expr/Cargo.toml
index 858dd86b7790d..1d543e3733163 100644
--- a/datafusion/physical-expr/Cargo.toml
+++ b/datafusion/physical-expr/Cargo.toml
@@ -41,6 +41,8 @@ workspace = true
 name = "datafusion_physical_expr"
 
 [features]
+# Exposes internal test utilities for use by other DataFusion crates.
+test_utils = []
 recursive_protection = ["dep:recursive"]
 # Forwards the `proto` feature to `datafusion-physical-expr-common`, exposing
 # `PhysicalExpr::to_proto` and letting expressions in this crate implement it.
@@ -71,6 +73,8 @@ half = { workspace = true }
 [dev-dependencies]
 arrow = { workspace = true, features = ["test_utils"] }
 criterion = { workspace = true }
+datafusion-common = { workspace = true, features = ["test_utils"] }
+datafusion-expr = { workspace = true, features = ["test_utils"] }
 datafusion-functions = { workspace = true }
 insta = { workspace = true }
 rand = { workspace = true }
diff --git a/datafusion/physical-expr/src/intervals/mod.rs b/datafusion/physical-expr/src/intervals/mod.rs
index 9752ca27b5a38..452213a1a3ccf 100644
--- a/datafusion/physical-expr/src/intervals/mod.rs
+++ b/datafusion/physical-expr/src/intervals/mod.rs
@@ -18,5 +18,13 @@
 //! Interval arithmetic and constraint propagation library
 
 pub mod cp_solver;
+/// # Public Only for Internal Use:
+/// Interval arithmetic helpers shared by tests in DataFusion crates. Not part of the
+/// supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+#[cfg(any(test, feature = "test_utils"))]
+#[doc(hidden)]
 pub mod test_utils;
 pub mod utils;
diff --git a/datafusion/physical-optimizer/Cargo.toml b/datafusion/physical-optimizer/Cargo.toml
index cb03303ac3c3f..f6389e4ea260e 100644
--- a/datafusion/physical-optimizer/Cargo.toml
+++ b/datafusion/physical-optimizer/Cargo.toml
@@ -58,5 +58,6 @@ recursive = { workspace = true, optional = true }
 datafusion-expr = { workspace = true }
 datafusion-functions = { workspace = true }
 datafusion-functions-window = { workspace = true }
+datafusion-physical-plan = { workspace = true, features = ["test_utils"] }
 insta = { workspace = true }
 tokio = { workspace = true }
diff --git a/datafusion/physical-plan/Cargo.toml b/datafusion/physical-plan/Cargo.toml
index 6a717defb95fa..4a37b15ccaea6 100644
--- a/datafusion/physical-plan/Cargo.toml
+++ b/datafusion/physical-plan/Cargo.toml
@@ -39,6 +39,7 @@ workspace = true
 
 [features]
 force_hash_collisions = []
+# Exposes internal test utilities for use by other DataFusion crates.
 test_utils = ["arrow/test_utils"]
 tokio_coop = []
 tokio_coop_fallback = []
@@ -93,8 +94,12 @@ tokio = { workspace = true, features = ["time"] }
 [dev-dependencies]
 arrow-data = { workspace = true }
 criterion = { workspace = true, features = ["async_futures"] }
+datafusion-common = { workspace = true, features = ["test_utils"] }
+datafusion-expr = { workspace = true, features = ["test_utils"] }
 datafusion-functions-aggregate = { workspace = true }
 datafusion-functions-window = { workspace = true }
+datafusion-physical-expr = { workspace = true, features = ["test_utils"] }
+datafusion-physical-plan = { workspace = true, features = ["test_utils"] }
 insta = { workspace = true }
 rand = { workspace = true }
 rstest = { workspace = true }
diff --git a/datafusion/physical-plan/src/distribution_requirements.rs b/datafusion/physical-plan/src/distribution_requirements.rs
index f7a17ddc7b8d6..17370789e34f4 100644
--- a/datafusion/physical-plan/src/distribution_requirements.rs
+++ b/datafusion/physical-plan/src/distribution_requirements.rs
@@ -188,6 +188,13 @@ impl InputDistributionRequirements {
     /// Independent per-child requirements are intentionally ignored here, use
     /// [`Self::child_satisfaction`] for those checks. An empty result means all
     /// co-partitioning requirements are satisfied.
+    ///
+    /// # Public Only for Internal Use:
+    /// `datafusion-physical-optimizer` uses this to enforce distribution
+    /// requirements. It is not part of the supported public API.
+    /// See the [API health policy] for details.
+    ///
+    /// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
     #[doc(hidden)]
     pub fn unsatisfied_co_partitioned_children(
         &self,
diff --git a/datafusion/physical-plan/src/joins/hash_join/mod.rs b/datafusion/physical-plan/src/joins/hash_join/mod.rs
index 7c1b0d76c2f73..198e0789b196b 100644
--- a/datafusion/physical-plan/src/joins/hash_join/mod.rs
+++ b/datafusion/physical-plan/src/joins/hash_join/mod.rs
@@ -18,7 +18,16 @@
 //! [`HashJoinExec`] Partitioned Hash Join Operator
 
 pub use exec::{HashJoinExec, HashJoinExecBuilder};
-pub use partitioned_hash_eval::{HashExpr, HashTableLookupExpr, SeededRandomState};
+/// # Public Only for Internal Use:
+/// Exposed for expression serialization tests in `datafusion-proto`. Not part of the
+/// supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+#[cfg(any(test, feature = "test_utils"))]
+#[doc(hidden)]
+pub use partitioned_hash_eval::HashTableLookupExpr;
+pub use partitioned_hash_eval::{HashExpr, SeededRandomState};
 
 mod exec;
 mod inlist_builder;
diff --git a/datafusion/physical-plan/src/joins/mod.rs b/datafusion/physical-plan/src/joins/mod.rs
index 10e5793e0ff32..b0ff814b87821 100644
--- a/datafusion/physical-plan/src/joins/mod.rs
+++ b/datafusion/physical-plan/src/joins/mod.rs
@@ -24,9 +24,16 @@ use arrow::array::BooleanBufferBuilder;
 pub use asof_join::{AsOfJoinExec, AsOfMatchExpr};
 pub use cross_join::CrossJoinExec;
 use datafusion_physical_expr::PhysicalExprRef;
-pub use hash_join::{
-    HashExpr, HashJoinExec, HashJoinExecBuilder, HashTableLookupExpr, SeededRandomState,
-};
+/// # Public Only for Internal Use:
+/// Exposed for expression serialization tests in `datafusion-proto`. Not part of the
+/// supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+#[cfg(any(test, feature = "test_utils"))]
+#[doc(hidden)]
+pub use hash_join::HashTableLookupExpr;
+pub use hash_join::{HashExpr, HashJoinExec, HashJoinExecBuilder, SeededRandomState};
 pub use nested_loop_join::{NestedLoopJoinExec, NestedLoopJoinExecBuilder};
 use parking_lot::Mutex;
 // Note: SortMergeJoin is not used in plans yet
@@ -51,9 +58,17 @@ mod array_map;
 mod join_filter;
 /// Hash map implementations for join operations.
 ///
-/// Note: This module is public for internal testing purposes only
-/// and is not guaranteed to be stable across versions.
+/// # Public Only for Internal Use:
+/// Exposed for hash join tests in `datafusion-proto`. Not part of the supported public
+/// API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+#[cfg(any(test, feature = "test_utils"))]
+#[doc(hidden)]
 pub mod join_hash_map;
+#[cfg(not(any(test, feature = "test_utils")))]
+mod join_hash_map;
 
 use array_map::ArrayMap;
 use utils::JoinHashMapType;
diff --git a/datafusion/physical-plan/src/lib.rs b/datafusion/physical-plan/src/lib.rs
index 5ff6cec374ee1..620648696a6fd 100644
--- a/datafusion/physical-plan/src/lib.rs
+++ b/datafusion/physical-plan/src/lib.rs
@@ -115,4 +115,11 @@ pub mod udaf {
     pub use datafusion_physical_expr::aggregate::AggregateFunctionExpr;
 }
 
+/// # Public Only for Internal Use:
+/// Shared test helpers for DataFusion crates. Not part of the supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+#[cfg(any(test, feature = "test_utils"))]
+#[doc(hidden)]
 pub mod test;
diff --git a/datafusion/physical-plan/src/spill/mod.rs b/datafusion/physical-plan/src/spill/mod.rs
index 3f56d2a6e0aaa..465e71b68de11 100644
--- a/datafusion/physical-plan/src/spill/mod.rs
+++ b/datafusion/physical-plan/src/spill/mod.rs
@@ -24,7 +24,13 @@ pub mod spill_pool;
 use datafusion_execution::spill_file::{AsyncSpillWriter, SpillWriter};
 // Moved for refactor, re-export to keep the public API stable
 pub use datafusion_common::utils::memory::get_record_batch_memory_size;
-// Re-export SpillManager for doctests only (hidden from public docs)
+/// # Public Only for Internal Use:
+/// Exposed here for doctests and the spilling tests in `datafusion`. Not part of the
+/// supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+#[cfg(any(test, feature = "test_utils"))]
 #[doc(hidden)]
 pub use spill_manager::SpillManager;
 
diff --git a/datafusion/proto/Cargo.toml b/datafusion/proto/Cargo.toml
index 4b11bea01103f..49bcde91c42bd 100644
--- a/datafusion/proto/Cargo.toml
+++ b/datafusion/proto/Cargo.toml
@@ -86,11 +86,14 @@ datafusion = { workspace = true, default-features = false, features = [
     "compression",
     "datetime_expressions",
     "nested_expressions",
+    "test_utils",
     "unicode_expressions",
 ] }
+datafusion-common = { workspace = true, features = ["test_utils"] }
 datafusion-functions = { workspace = true, default-features = true }
 datafusion-functions-aggregate = { workspace = true }
 datafusion-functions-window-common = { workspace = true }
+datafusion-physical-plan = { workspace = true, features = ["test_utils"] }
 doc-comment = { workspace = true }
 flate2 = { workspace = true }
 pretty_assertions = "1.4"
diff --git a/datafusion/pruning/Cargo.toml b/datafusion/pruning/Cargo.toml
index a914a0a079bcd..dcb557d750cf4 100644
--- a/datafusion/pruning/Cargo.toml
+++ b/datafusion/pruning/Cargo.toml
@@ -27,6 +27,7 @@ log = { workspace = true }
 
 [dev-dependencies]
 criterion = { workspace = true }
+datafusion-common = { workspace = true, features = ["test_utils"] }
 datafusion-expr = { workspace = true }
 datafusion-functions-nested = { workspace = true }
 insta = { workspace = true }
diff --git a/datafusion/spark/Cargo.toml b/datafusion/spark/Cargo.toml
index 08309a931d96b..a931deedcddcc 100644
--- a/datafusion/spark/Cargo.toml
+++ b/datafusion/spark/Cargo.toml
@@ -73,6 +73,7 @@ arrow = { workspace = true, features = ["test_utils"] }
 criterion = { workspace = true }
 # for SessionStateBuilderSpark tests
 datafusion = { workspace = true, default-features = false, features = ["sql"] }
+datafusion-common = { workspace = true, features = ["test_utils"] }
 tokio = { workspace = true, features = ["rt"] }
 
 [[bench]]
diff --git a/datafusion/sql/Cargo.toml b/datafusion/sql/Cargo.toml
index 318f8934639aa..8234371b70e1f 100644
--- a/datafusion/sql/Cargo.toml
+++ b/datafusion/sql/Cargo.toml
@@ -67,6 +67,8 @@ stacker = { workspace = true, optional = true }
 [dev-dependencies]
 ctor = { workspace = true }
 # please do not move these dependencies to the main dependencies section
+datafusion-common = { workspace = true, features = ["test_utils"] }
+datafusion-expr = { workspace = true, features = ["test_utils"] }
 datafusion-functions = { workspace = true, default-features = true }
 datafusion-functions-aggregate = { workspace = true }
 datafusion-functions-nested = { workspace = true, features = ["sql"] }
diff --git a/datafusion/sqllogictest/Cargo.toml b/datafusion/sqllogictest/Cargo.toml
index c43f78f846092..e004065c6abea 100644
--- a/datafusion/sqllogictest/Cargo.toml
+++ b/datafusion/sqllogictest/Cargo.toml
@@ -46,7 +46,7 @@ bigdecimal = { workspace = true }
 bytes = { workspace = true, optional = true }
 chrono = { workspace = true, optional = true }
 clap = { version = "4.5.60", features = ["derive", "env"] }
-datafusion = { workspace = true, default-features = true, features = ["avro"] }
+datafusion = { workspace = true, default-features = true, features = ["test_utils", "avro"] }
 datafusion-spark = { workspace = true, features = ["core"] }
 datafusion-substrait = { workspace = true, default-features = true, optional = true }
 futures = { workspace = true }
diff --git a/datafusion/substrait/Cargo.toml b/datafusion/substrait/Cargo.toml
index a0f203cec8db6..77af9186684fc 100644
--- a/datafusion/substrait/Cargo.toml
+++ b/datafusion/substrait/Cargo.toml
@@ -49,7 +49,7 @@ url = { workspace = true }
 tokio = { workspace = true, features = ["fs"] }
 
 [dev-dependencies]
-datafusion = { workspace = true, features = ["nested_expressions", "unicode_expressions"] }
+datafusion = { workspace = true, features = ["test_utils", "nested_expressions", "unicode_expressions"] }
 datafusion-functions-aggregate = { workspace = true }
 serde_json = { workspace = true }
 tokio = { workspace = true }
diff --git a/datafusion/wasmtest/Cargo.toml b/datafusion/wasmtest/Cargo.toml
index d6cea2e68d384..7e509e495c59c 100644
--- a/datafusion/wasmtest/Cargo.toml
+++ b/datafusion/wasmtest/Cargo.toml
@@ -61,6 +61,7 @@ wasm-bindgen = "0.2.99"
 
 [dev-dependencies]
 bytes = { workspace = true }
+datafusion-common = { workspace = true, features = ["test_utils"] }
 futures = { workspace = true }
 object_store = { workspace = true }
 # needs to be compiled
diff --git a/docs/source/contributor-guide/api-health.md b/docs/source/contributor-guide/api-health.md
index 8737df280f4f8..ad0c6118a6916 100644
--- a/docs/source/contributor-guide/api-health.md
+++ b/docs/source/contributor-guide/api-health.md
@@ -43,6 +43,10 @@ Examples of non-breaking changes include:
 - Marking a function as deprecated (`#[deprecated]`)
 - Adding a new function to a `trait` with a default implementation
 
+<!-- Keep this anchor stable: Rustdoc comments link to this section. -->
+
+<a name="datafusion-internal-public-apis"></a>
+
 ### DataFusion-internal Public APIs
 
 Some internal implementation details require `pub` visibility because they are
@@ -51,24 +55,58 @@ extension points. They are hidden from generated documentation and are not part
 of DataFusion's supported public API, so they may be changed or removed without
 notice or a deprecation period. Examples include:
 
-1. Test helpers.
-2. Operator APIs required by the optimizer to inspect or rewrite execution plans
-   across crate boundaries.
+1. Test/micro-benchmark helpers.
+2. Internal utilities, such as operator APIs required by the optimizer to inspect
+   or rewrite execution plans across crate boundaries.
+
+Note: Exposing internal APIs for tests or microbenchmarks is not recommended,
+though some legacy code does so. For new tests and benchmarks, prefer exercising
+observable behavior to simplify maintenance.
+
+#### Test Helpers
+
+Hide shared test helpers with `#[doc(hidden)]` and gate them behind the non-default
+`test_utils` feature, declared as `test_utils = []` in `[features]`. Unit tests use
+`cfg(test)`; tests and benchmarks that link the crate enable `test_utils` in
+`[dev-dependencies]`.
+
+```txt
+/// # Public Only for Internal Use:
+/// Shared test helpers for DataFusion crates. Not part of the supported public API.
+/// See the [API health policy] for details.
+///
+/// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
+#[cfg(any(test, feature = "test_utils"))]
+#[doc(hidden)]
+pub mod test;
+```
+
+```toml
+[dev-dependencies]
+datafusion-physical-plan = { workspace = true, features = ["test_utils"] }
+```
+
+#### Internal Utilities
+
+Utilities needed across crates during normal execution cannot be gated behind
+`test_utils`. Add `#[doc(hidden)]` and a doc comment section headed 
+`# Public Only for Internal Use:`. Name the crate or component that requires access 
+and explain why the API is not intended for downstream use.
 
-For APIs intended only for internal use, add `#[doc(hidden)]` and a doc comment
-section headed `# Public Only for Internal Use:`. Name the crate or component
-that requires access and explain why the API is not intended for downstream use.
 For example:
 
 ```txt
-impl HashTableLookupExpr {
+impl InputDistributionRequirements {
     /// ...
     ///
     /// # Public Only for Internal Use:
-    /// `datafusion-proto` tests require this constructor, but it is not part of
-    /// the supported public API.
+    /// `datafusion-physical-optimizer` uses this to enforce distribution
+    /// requirements. It is not part of the supported public API.
+    /// See the [API health policy] for details.
+    ///
+    /// [API health policy]: https://datafusion.apache.org/contributor-guide/api-health.html#datafusion-internal-public-apis
     #[doc(hidden)]
-    pub fn new(...) {...}
+    pub fn unsatisfied_co_partitioned_children(...) {...}
 }
 ```