diff --git a/tests/test_edge_cases.py b/tests/test_edge_cases.py
new file mode 100644
index 0000000..99cae25
--- /dev/null
+++ b/tests/test_edge_cases.py
@@ -0,0 +1,76 @@
+"""Edge case tests for all tokenizer variants."""
+
+import pytest
+
+from complex_tokenization.tokenizer import (
+    BNETokenizer,
+    BoundlessBPETokenizer,
+    BPETokenizer,
+    SuperBPETokenizer,
+)
+
+ALL_TOKENIZERS = [
+    ("BPE", lambda: BPETokenizer()),
+    ("BNE", lambda: BNETokenizer(n=4)),
+    ("Boundless", lambda: BoundlessBPETokenizer()),
+    ("Super", lambda: SuperBPETokenizer(disconnected_merges=2)),
+]
+
+
+class TestEmptyAndMinimal:
+    @pytest.mark.parametrize(("name", "factory"), ALL_TOKENIZERS, ids=[t[0] for t in ALL_TOKENIZERS])
+    def test_empty_text(self, name, factory):
+        tok = factory()
+        merges = tok.train([""], num_merges=10)
+        assert merges == []
+
+    @pytest.mark.parametrize(("name", "factory"), ALL_TOKENIZERS, ids=[t[0] for t in ALL_TOKENIZERS])
+    def test_single_char(self, name, factory):
+        tok = factory()
+        merges = tok.train(["a"], num_merges=10)
+        assert merges == []
+
+    @pytest.mark.parametrize(("name", "factory"), ALL_TOKENIZERS, ids=[t[0] for t in ALL_TOKENIZERS])
+    def test_single_word(self, name, factory):
+        tok = factory()
+        merges = tok.train(["hello"], num_merges=2)
+        assert len(merges) <= 2
+
+    @pytest.mark.parametrize(("name", "factory"), ALL_TOKENIZERS, ids=[t[0] for t in ALL_TOKENIZERS])
+    def test_all_same_chars(self, name, factory):
+        tok = factory()
+        merges = tok.train(["aaaaaaaaaa"], num_merges=5)
+        assert len(merges) >= 1
+        assert all(t == 'a' for t in merges[0])
+
+    @pytest.mark.parametrize(("name", "factory"), ALL_TOKENIZERS, ids=[t[0] for t in ALL_TOKENIZERS])
+    def test_whitespace_only(self, name, factory):
+        tok = factory()
+        merges = tok.train(["   "], num_merges=5)
+        assert len(merges) >= 1
+
+    @pytest.mark.parametrize(("name", "factory"), ALL_TOKENIZERS, ids=[t[0] for t in ALL_TOKENIZERS])
+    def test_multiple_empty_texts(self, name, factory):
+        tok = factory()
+        merges = tok.train(["", "", ""], num_merges=5)
+        assert merges == []
+
+
+class TestUnicodeEdgeCases:
+    @pytest.mark.parametrize(("name", "factory"), ALL_TOKENIZERS, ids=[t[0] for t in ALL_TOKENIZERS])
+    def test_emoji(self, name, factory):
+        tok = factory()
+        merges = tok.train(["👋👋👋"], num_merges=3)
+        assert len(merges) >= 1
+
+    @pytest.mark.parametrize(("name", "factory"), ALL_TOKENIZERS, ids=[t[0] for t in ALL_TOKENIZERS])
+    def test_mixed_scripts(self, name, factory):
+        tok = factory()
+        merges = tok.train(["hello שלום 你好 hello שלום 你好"], num_merges=5)
+        assert len(merges) >= 1
+
+    @pytest.mark.parametrize(("name", "factory"), ALL_TOKENIZERS, ids=[t[0] for t in ALL_TOKENIZERS])
+    def test_newlines(self, name, factory):
+        tok = factory()
+        merges = tok.train(["hello\nworld\nhello\nworld"], num_merges=3)
+        assert len(merges) >= 1