diff --git a/tests/test_cli.py b/tests/test_cli.py
new file mode 100644
index 0000000..fabdc2c
--- /dev/null
+++ b/tests/test_cli.py
@@ -0,0 +1,253 @@
+"""Tests for the CLI interface."""
+
+import json
+import pytest
+from click.testing import CliRunner
+from regex_humanizer.cli import main, explain, test, flavors, validate, convert
+
+
+class TestCLIMain:
+    """Test the main CLI entry point."""
+
+    def test_main_help(self):
+        """Test that main help works."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["--help"])
+
+        assert result.exit_code == 0
+        assert "Regex Humanizer" in result.output
+        assert "explain" in result.output
+        assert "test" in result.output
+        assert "interactive" in result.output
+
+
+class TestCLIExplain:
+    """Test the explain command."""
+
+    def test_explain_simple_literal(self):
+        """Test explaining a simple literal."""
+        runner = CliRunner()
+        result = runner.invoke(explain, ["hello"])
+
+        assert result.exit_code == 0
+        assert "Pattern" in result.output or "hello" in result.output
+
+    def test_explain_with_flavor_option(self):
+        """Test explaining with a flavor option."""
+        runner = CliRunner()
+        result = runner.invoke(explain, ["--flavor", "javascript", "test"])
+
+        assert result.exit_code == 0
+        assert "Flavor" in result.output or "javascript" in result.output
+
+    def test_explain_with_json_output(self):
+        """Test explaining with JSON output."""
+        runner = CliRunner()
+        result = runner.invoke(explain, ["--output", "json", "\\d+"])
+
+        assert result.exit_code == 0
+        assert "{", "}" in result.output
+
+    def test_explain_with_verbose(self):
+        """Test explaining with verbose flag."""
+        runner = CliRunner()
+        result = runner.invoke(explain, ["--verbose", "\\d+"])
+
+        assert result.exit_code == 0
+        assert "Features" in result.output or "digit" in result.output.lower()
+
+    def test_explain_complex_pattern(self):
+        """Test explaining a complex pattern."""
+        runner = CliRunner()
+        pattern = r"^(?:http|https)://[\w.-]+\.(?:com|org|net)$"
+        result = runner.invoke(explain, [pattern])
+
+        assert result.exit_code == 0
+        assert "Pattern" in result.output
+
+    def test_explain_phone_pattern(self):
+        """Test explaining a phone pattern."""
+        runner = CliRunner()
+        result = runner.invoke(explain, [r"\d{3}-\d{4}"])
+
+        assert result.exit_code == 0
+
+    def test_explain_character_class(self):
+        """Test explaining a character class."""
+        runner = CliRunner()
+        result = runner.invoke(explain, ["[a-zA-Z]+"])
+
+        assert result.exit_code == 0
+
+
+class TestCLITest:
+    """Test the test command."""
+
+    def test_test_simple_literal(self):
+        """Test generating test cases for a simple literal."""
+        runner = CliRunner()
+        result = runner.invoke(test, ["hello"])
+
+        assert result.exit_code == 0
+        assert "Matching" in result.output or "hello" in result.output
+        assert "Non-matching" in result.output
+
+    def test_test_with_count_option(self):
+        """Test generating a specific number of test cases."""
+        runner = CliRunner()
+        result = runner.invoke(test, ["--count", "3", "a"])
+
+        assert result.exit_code == 0
+
+    def test_test_with_json_output(self):
+        """Test generating test cases with JSON output."""
+        runner = CliRunner()
+        result = runner.invoke(test, ["--output", "json", "test"])
+
+        assert result.exit_code == 0
+        data = json.loads(result.output)
+        assert "matching" in data
+        assert "non_matching" in data
+
+    def test_test_phone_pattern(self):
+        """Test generating test cases for a phone pattern."""
+        runner = CliRunner()
+        result = runner.invoke(test, [r"\d{3}-\d{4}"])
+
+        assert result.exit_code == 0
+        assert "Matching" in result.output
+
+    def test_test_email_pattern(self):
+        """Test generating test cases for an email pattern."""
+        runner = CliRunner()
+        result = runner.invoke(test, [r"[a-z]+@[a-z]+\.[a-z]+"])
+
+        assert result.exit_code == 0
+
+    def test_test_quantifier_pattern(self):
+        """Test generating test cases for a quantifier pattern."""
+        runner = CliRunner()
+        result = runner.invoke(test, ["a{2,4}"])
+
+        assert result.exit_code == 0
+
+
+class TestCLIFlavors:
+    """Test the flavors command."""
+
+    def test_flavors_list(self):
+        """Test listing available flavors."""
+        runner = CliRunner()
+        result = runner.invoke(flavors)
+
+        assert result.exit_code == 0
+        assert "pcre" in result.output.lower()
+        assert "javascript" in result.output.lower()
+        assert "python" in result.output.lower()
+
+
+class TestCLIValidate:
+    """Test the validate command."""
+
+    def test_validate_valid_pattern(self):
+        """Test validating a valid pattern."""
+        runner = CliRunner()
+        result = runner.invoke(validate, ["hello"])
+
+        assert result.exit_code == 0
+        assert "PASSED" in result.output or "Validation" in result.output
+
+    def test_validate_with_flavor(self):
+        """Test validating with a specific flavor."""
+        runner = CliRunner()
+        result = runner.invoke(validate, ["--flavor", "javascript", "test"])
+
+        assert result.exit_code == 0
+
+    def test_validate_complex_pattern(self):
+        """Test validating a complex pattern."""
+        runner = CliRunner()
+        pattern = r"^(?:http|https)://[\w.-]+\.(?:com|org|net)$"
+        result = runner.invoke(validate, [pattern])
+
+        assert result.exit_code == 0
+
+
+class TestCLIConvert:
+    """Test the convert command."""
+
+    def test_convert_pcre_to_js(self):
+        """Test converting a pattern from PCRE to JavaScript."""
+        runner = CliRunner()
+        result = runner.invoke(convert, ["(?P<test>hello)", "--from-flavor", "pcre", "--to-flavor", "javascript"])
+
+        assert result.exit_code == 0
+        assert "Converted" in result.output
+
+    def test_convert_with_defaults(self):
+        """Test converting with default flavors."""
+        runner = CliRunner()
+        result = runner.invoke(convert, ["test"])
+
+        assert result.exit_code == 0
+        assert "Original" in result.output
+        assert "Converted" in result.output
+
+
+class TestCLIInteractive:
+    """Test the interactive command."""
+
+    def test_interactive_command_exists(self):
+        """Test that interactive command is available."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["interactive", "--help"])
+
+        assert result.exit_code == 0
+        assert "interactive" in result.output.lower()
+
+    def test_interactive_with_flavor(self):
+        """Test interactive mode with a specific flavor."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["interactive", "--flavor", "python"])
+
+        assert result.exit_code == 0
+
+
+class TestCLIIntegration:
+    """Integration tests for CLI."""
+
+    def test_flavor_option_global(self):
+        """Test that global flavor option works."""
+        runner = CliRunner()
+        result = runner.invoke(main, ["--flavor", "python", "explain", "test"])
+
+        assert result.exit_code == 0
+
+    def test_error_handling_invalid_pattern(self):
+        """Test error handling for invalid patterns."""
+        runner = CliRunner()
+        result = runner.invoke(explain, ["["])
+
+        assert result.exit_code == 0
+
+    def test_output_json_structure(self):
+        """Test JSON output has correct structure."""
+        runner = CliRunner()
+        result = runner.invoke(explain, ["--output", "json", "\\d+"])
+
+        assert result.exit_code == 0
+        data = json.loads(result.output)
+        assert "pattern" in data
+        assert "flavor" in data
+        assert "explanation" in data
+
+    def test_output_test_json_structure(self):
+        """Test JSON test output has correct structure."""
+        runner = CliRunner()
+        result = runner.invoke(test, ["--output", "json", "\\d"])
+
+        assert result.exit_code == 0
+        data = json.loads(result.output)
+        assert "pattern" in data
+        assert "matching" in data
+        assert "non_matching" in data