feat: Add Caesar cipher dataset generator with encryption and decryption tasks

tests/test_caesar_cipher.py

@@ -0,0 +1,107 @@
+"""Tests for Caesar cipher task generation"""
+
+import pytest
+
+from reasoning_gym.algorithmic.caesar_cipher import CaesarCipherConfig, CaesarCipherDataset
+
+
+def test_caesar_cipher_config_validation():
+    """Test that invalid configs raise appropriate errors"""
+    with pytest.raises(AssertionError):
+        config = CaesarCipherConfig(min_words=0)
+        config.validate()
+
+    with pytest.raises(AssertionError):
+        config = CaesarCipherConfig(min_words=10, max_words=5)
+        config.validate()
+
+    with pytest.raises(AssertionError):
+        config = CaesarCipherConfig(min_rotation=0)
+        config.validate()
+
+    with pytest.raises(AssertionError):
+        config = CaesarCipherConfig(max_rotation=26)
+        config.validate()
+
+
+def test_caesar_cipher_deterministic():
+    """Test that dataset generates same items with same seed"""
+    config = CaesarCipherConfig(seed=42, size=10)
+    dataset1 = CaesarCipherDataset(config)
+    dataset2 = CaesarCipherDataset(config)
+
+    for i in range(len(dataset1)):
+        assert dataset1[i] == dataset2[i]
+
+
+def test_caesar_cipher_encryption():
+    """Test the Caesar cipher encryption logic"""
+    config = CaesarCipherConfig(size=1, seed=42)
+    dataset = CaesarCipherDataset(config)
+    
+    # Test with known rotation
+    text = "HELLO"
+    encrypted = dataset._caesar_encrypt(text, 1)
+    assert encrypted == "IFMMP"  # Each letter shifted by 1
+
+    # Test wrapping around Z
+    encrypted = dataset._caesar_encrypt("XYZ", 2)
+    assert encrypted == "ZAB"
+
+    # Test preserving spaces
+    encrypted = dataset._caesar_encrypt("HELLO WORLD", 1)
+    assert encrypted == "IFMMP XPSME"
+
+
+def test_caesar_cipher_dataset_items():
+    """Test basic properties of generated items"""
+    config = CaesarCipherConfig(
+        min_words=3,
+        max_words=5,
+        min_rotation=1,
+        max_rotation=3,
+        size=10,
+        seed=42
+    )
+    dataset = CaesarCipherDataset(config)
+
+    for i in range(len(dataset)):
+        item = dataset[i]
+        
+        # Check item structure
+        assert isinstance(item, dict)
+        assert "question" in item
+        assert "answer" in item
+        assert "metadata" in item
+        
+        # Check metadata
+        assert "rotation" in item["metadata"]
+        assert "cipher_text" in item["metadata"]
+        assert "clear_text" in item["metadata"]
+        
+        # Verify rotation constraints
+        rotation = item["metadata"]["rotation"]
+        assert config.min_rotation <= rotation <= config.max_rotation
+        
+        # Verify text properties
+        clear_text = item["metadata"]["clear_text"]
+        words = clear_text.split()
+        assert config.min_words <= len(words) <= config.max_words
+        assert all(word.isupper() and word.isalpha() for word in words)
+
+        # Verify encryption
+        cipher_text = item["metadata"]["cipher_text"]
+        decrypted = dataset._caesar_encrypt(cipher_text, -rotation)  # Decrypt by negative rotation
+        assert decrypted == clear_text
+
+
+def test_caesar_cipher_iteration():
+    """Test that iteration respects dataset size"""
+    config = CaesarCipherConfig(size=5, seed=42)
+    dataset = CaesarCipherDataset(config)
+
+    items = list(dataset)
+    assert len(items) == config.size
+
+    # Test multiple iterations yield same items
+    assert items == list(dataset)