diff --git a/shellhist/tests/test_patterns.py b/shellhist/tests/test_patterns.py
new file mode 100644
index 0000000..a437709
--- /dev/null
+++ b/shellhist/tests/test_patterns.py
@@ -0,0 +1,183 @@
+"""Tests for pattern detection algorithms."""
+
+import pytest
+
+from shellhist.core import HistoryEntry, HistoryStore
+from shellhist.core.patterns import (
+    ngram_analysis,
+    detect_repetitive_commands,
+    detect_command_pairs,
+    detect_command_triplets,
+    detect_common_sequences,
+)
+
+
+class TestNgramAnalysis:
+    """Test n-gram analysis functionality."""
+
+    def test_empty_store(self):
+        """Test with empty store."""
+        store = HistoryStore()
+        results = ngram_analysis(store, n=2)
+        
+        assert len(results) == 0
+
+    def test_simple_pairs(self):
+        """Test detecting command pairs."""
+        store = HistoryStore()
+        
+        commands = [
+            "git status",
+            "git log",
+            "git status",
+            "git log",
+        ]
+        
+        for cmd in commands:
+            store.add_entry(HistoryEntry(command=cmd))
+        
+        results = ngram_analysis(store, n=2)
+        
+        assert len(results) > 0
+        pair = results[0]
+        assert "git status -> git log" in " -> ".join(pair.commands)
+
+    def test_triplets(self):
+        """Test detecting command triplets."""
+        store = HistoryStore()
+        
+        commands = [
+            "git add .",
+            "git commit",
+            "git push",
+            "git add .",
+            "git commit",
+            "git push",
+        ]
+        
+        for cmd in commands:
+            store.add_entry(HistoryEntry(command=cmd))
+        
+        results = ngram_analysis(store, n=3)
+        
+        assert len(results) == 1
+        assert results[0].frequency == 2
+
+    def test_min_frequency_filter(self):
+        """Test minimum frequency filtering."""
+        store = HistoryStore()
+        
+        commands = [
+            "git status",
+            "ls",
+            "git status",
+        ]
+        
+        for cmd in commands:
+            store.add_entry(HistoryEntry(command=cmd))
+        
+        results = ngram_analysis(store, n=2, min_frequency=3)
+        
+        assert len(results) == 0
+
+
+class TestDetectRepetitiveCommands:
+    """Test repetitive command detection."""
+
+    def test_detect_repetitive(self):
+        """Test detecting repetitive single commands."""
+        store = HistoryStore()
+        
+        for _ in range(5):
+            store.add_entry(HistoryEntry(command="git status"))
+        
+        for _ in range(2):
+            store.add_entry(HistoryEntry(command="ls"))
+        
+        results = detect_repetitive_commands(store, min_frequency=3)
+        
+        assert len(results) == 1
+        assert results[0].commands == ("git status",)
+        assert results[0].frequency == 5
+
+    def test_no_repetitive_commands(self):
+        """Test when no commands are repetitive."""
+        store = HistoryStore()
+        
+        for cmd in ["git status", "ls", "pwd"]:
+            store.add_entry(HistoryEntry(command=cmd))
+        
+        results = detect_repetitive_commands(store, min_frequency=3)
+        
+        assert len(results) == 0
+
+
+class TestDetectCommandPairs:
+    """Test command pair detection."""
+
+    def test_detect_pairs(self):
+        """Test detecting command pairs."""
+        store = HistoryStore()
+        
+        commands = [
+            "git add .",
+            "git commit",
+            "git add .",
+            "git commit",
+        ]
+        
+        for cmd in commands:
+            store.add_entry(HistoryEntry(command=cmd))
+        
+        results = detect_command_pairs(store, min_frequency=2)
+        
+        assert len(results) == 1
+
+
+class TestDetectCommandTriplets:
+    """Test command triplet detection."""
+
+    def test_detect_triplets(self):
+        """Test detecting command triplets."""
+        store = HistoryStore()
+        
+        commands = [
+            "git add .",
+            "git commit",
+            "git push",
+            "git add .",
+            "git commit",
+            "git push",
+        ]
+        
+        for cmd in commands:
+            store.add_entry(HistoryEntry(command=cmd))
+        
+        results = detect_command_triplets(store, min_frequency=2)
+        
+        assert len(results) == 1
+        assert len(results[0].commands) == 3
+
+
+class TestDetectCommonSequences:
+    """Test common sequence detection."""
+
+    def test_detect_sequences_various_lengths(self):
+        """Test detecting sequences of various lengths."""
+        store = HistoryStore()
+        
+        commands = [
+            "git add .",
+            "git commit",
+            "git push",
+            "git add .",
+            "git commit",
+            "git push",
+        ]
+        
+        for cmd in commands:
+            store.add_entry(HistoryEntry(command=cmd))
+        
+        results = detect_common_sequences(store, max_length=3, min_occurrences=2)
+        
+        assert len(results) > 0