test: add pytest tests for template validator

Comprehensive test suite covering glob validation, trailing
whitespace detection, duplicate and conflict detection,
coverage analysis, and report formatting.

Signed-off-by: Srikanth Patchava <spatchava@meta.com>

scripts/test_validate_templates.py

@@ -0,0 +1,189 @@
+#!/usr/bin/env python3
+"""Tests for the gitignore template validator."""
+
+import os
+import tempfile
+import pytest
+
+from validate_templates import (
+    Issue,
+    Severity,
+    ValidationReport,
+    analyze_coverage,
+    check_trailing_whitespace,
+    discover_templates,
+    find_conflicts,
+    find_duplicates,
+    format_report,
+    is_valid_glob_pattern,
+    validate_template,
+)
+
+
+class TestIsValidGlobPattern:
+    def test_simple_extension(self):
+        assert is_valid_glob_pattern("*.py") is True
+
+    def test_directory_pattern(self):
+        assert is_valid_glob_pattern("build/") is True
+
+    def test_negation(self):
+        assert is_valid_glob_pattern("!important.txt") is True
+
+    def test_double_star(self):
+        assert is_valid_glob_pattern("**/logs") is True
+
+    def test_bracket_pattern(self):
+        assert is_valid_glob_pattern("*.[oa]") is True
+
+    def test_unmatched_bracket(self):
+        assert is_valid_glob_pattern("*.[o") is False
+
+    def test_empty_after_strip(self):
+        assert is_valid_glob_pattern("!") is False
+
+    def test_rooted_pattern(self):
+        assert is_valid_glob_pattern("/build") is True
+
+
+class TestCheckTrailingWhitespace:
+    def test_no_trailing(self):
+        assert check_trailing_whitespace("*.py", 1) is None
+
+    def test_with_trailing_space(self):
+        issue = check_trailing_whitespace("*.py ", 5)
+        assert issue is not None
+        assert issue.severity == Severity.WARNING
+        assert issue.line_number == 5
+
+    def test_blank_line_ignored(self):
+        assert check_trailing_whitespace("   ", 1) is None
+
+
+class TestFindDuplicates:
+    def test_no_duplicates(self):
+        patterns = [(1, "*.py"), (2, "*.js"), (3, "build/")]
+        assert find_duplicates(patterns) == []
+
+    def test_exact_duplicate(self):
+        patterns = [(1, "*.py"), (2, "*.js"), (3, "*.py")]
+        issues = find_duplicates(patterns)
+        assert len(issues) == 1
+        assert issues[0].line_number == 3
+
+    def test_trailing_slash_normalization(self):
+        patterns = [(1, "build"), (2, "build/")]
+        issues = find_duplicates(patterns)
+        assert len(issues) == 1
+
+
+class TestFindConflicts:
+    def test_no_conflicts(self):
+        patterns = [(1, "*.log"), (2, "*.tmp")]
+        assert find_conflicts(patterns) == []
+
+    def test_include_then_negate(self):
+        patterns = [(1, "*.log"), (2, "!*.log")]
+        issues = find_conflicts(patterns)
+        assert len(issues) == 1
+        assert issues[0].severity == Severity.WARNING
+
+    def test_negate_without_include(self):
+        patterns = [(1, "!important.txt")]
+        issues = find_conflicts(patterns)
+        assert len(issues) == 0
+
+
+class TestAnalyzeCoverage:
+    def test_many_wildcards(self):
+        patterns = [(i, f"*.ext{i}") for i in range(12)]
+        issues = analyze_coverage(patterns)
+        msgs = [i.message for i in issues]
+        assert any("wildcard" in m for m in msgs)
+
+    def test_no_directory_patterns(self):
+        patterns = [(i, f"*.ext{i}") for i in range(6)]
+        issues = analyze_coverage(patterns)
+        msgs = [i.message for i in issues]
+        assert any("directory" in m.lower() for m in msgs)
+
+    def test_duplicate_extension_suggestion(self):
+        patterns = [(1, "*.py"), (2, "*.py")]
+        issues = analyze_coverage(patterns)
+        msgs = [i.message for i in issues]
+        assert any(".py" in m for m in msgs)
+
+
+class TestValidateTemplate:
+    def test_valid_template(self):
+        with tempfile.NamedTemporaryFile(
+            mode="w", suffix=".gitignore", delete=False
+        ) as f:
+            f.write("# Build output\nbuild/\n*.o\n*.a\n")
+            f.flush()
+            report = validate_template(f.name)
+        os.unlink(f.name)
+        assert report.error_count == 0
+        assert report.pattern_count == 3
+        assert report.comment_count == 1
+
+    def test_invalid_pattern(self):
+        with tempfile.NamedTemporaryFile(
+            mode="w", suffix=".gitignore", delete=False
+        ) as f:
+            f.write("*.[invalid\n")
+            f.flush()
+            report = validate_template(f.name)
+        os.unlink(f.name)
+        assert report.error_count > 0
+
+    def test_file_not_found(self):
+        report = validate_template("/nonexistent/file.gitignore")
+        assert report.error_count > 0
+
+
+class TestFormatReport:
+    def test_clean_report(self):
+        report = ValidationReport(
+            template_file="test.gitignore",
+            total_lines=5,
+            pattern_count=3,
+            comment_count=1,
+            blank_count=1,
+        )
+        output = format_report(report)
+        assert "No issues found" in output
+
+    def test_report_with_issues(self):
+        report = ValidationReport(
+            template_file="test.gitignore",
+            total_lines=5,
+            pattern_count=3,
+        )
+        report.issues.append(
+            Issue(
+                severity=Severity.ERROR,
+                line_number=2,
+                line_content="*.[bad",
+                message="Invalid glob pattern",
+            )
+        )
+        output = format_report(report, verbose=True)
+        assert "ERROR" in output
+        assert "*.[bad" in output
+
+
+class TestDiscoverTemplates:
+    def test_discover_in_directory(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Create fake gitignore files
+            for name in ["Python.gitignore", "Java.gitignore", "README.md"]:
+                with open(os.path.join(tmpdir, name), "w") as f:
+                    f.write("# test\n")
+            templates = discover_templates(tmpdir)
+            assert len(templates) == 2
+            assert all(t.endswith(".gitignore") for t in templates)
+
+
+if __name__ == "__main__":
+    pytest.main([__file__, "-v"])