diff --git a/tests/integration/test_end_to_end.py b/tests/integration/test_end_to_end.py
new file mode 100644
index 0000000..bb51c75
--- /dev/null
+++ b/tests/integration/test_end_to_end.py
@@ -0,0 +1,124 @@
+"""Integration tests for LogLens."""
+
+import pytest
+import tempfile
+from pathlib import Path
+
+from loglens.parsers.base import LogFormat
+from loglens.analyzers.analyzer import LogAnalyzer
+from loglens.formatters.table_formatter import TableFormatter
+from loglens.formatters.json_formatter import JSONFormatter
+
+
+class TestEndToEnd:
+    """End-to-end integration tests."""
+
+    def test_json_file_analysis(self, tmp_path):
+        """Test complete JSON file analysis."""
+        log_content = """{"timestamp": "2024-01-15T10:30:00Z", "level": "INFO", "message": "App started"}
+{"timestamp": "2024-01-15T10:30:01Z", "level": "ERROR", "message": "Connection failed"}
+{"timestamp": "2024-01-15T10:30:02Z", "level": "WARNING", "message": "Deprecated API"}
+"""
+        log_file = tmp_path / "app.log"
+        log_file.write_text(log_content)
+
+        analyzer = LogAnalyzer()
+        result = analyzer.analyze_file(str(log_file))
+
+        assert result.format_detected == LogFormat.JSON
+        assert result.total_lines == 3
+        assert result.parsed_count == 3
+        assert result.error_count == 1
+        assert result.warning_count == 1
+
+    def test_syslog_file_analysis(self, tmp_path):
+        """Test complete syslog file analysis."""
+        log_content = """Jan 15 10:30:00 server-01 systemd[1]: Started Application.
+Jan 15 10:30:01 server-01 app[1234]: ERROR: Database connection failed
+Jan 15 10:30:02 server-01 app[1234]: WARNING: High memory usage
+"""
+        log_file = tmp_path / "syslog.log"
+        log_file.write_text(log_content)
+
+        analyzer = LogAnalyzer()
+        result = analyzer.analyze_file(str(log_file))
+
+        assert result.format_detected == LogFormat.SYSLOG
+        assert result.parsed_count == 3
+
+    def test_apache_file_analysis(self, tmp_path):
+        """Test complete Apache file analysis."""
+        log_content = '''192.168.1.1 - - [15/Jan/2024:10:30:00 +0000] "GET /api/users HTTP/1.1" 200 1234
+192.168.1.2 - - [15/Jan/2024:10:30:01 +0000] "POST /api/login HTTP/1.1" 401 567
+192.168.1.3 - - [15/Jan/2024:10:30:02 +0000] "GET /api/orders HTTP/1.1" 500 4321
+'''
+        log_file = tmp_path / "apache.log"
+        log_file.write_text(log_content)
+
+        analyzer = LogAnalyzer()
+        result = analyzer.analyze_file(str(log_file))
+
+        assert result.format_detected == LogFormat.APACHE
+        assert result.error_count == 1
+        assert result.warning_count == 1
+
+    def test_json_output_format(self, tmp_path):
+        """Test JSON output formatting."""
+        log_content = '{"level": "INFO", "message": "Test"}\n'
+        log_file = tmp_path / "test.log"
+        log_file.write_text(log_content)
+
+        analyzer = LogAnalyzer()
+        result = analyzer.analyze_file(str(log_file))
+
+        formatter = JSONFormatter()
+        json_output = formatter.format(result)
+
+        assert "json" in json_output.lower() or "parsed" in json_output.lower()
+
+    def test_error_detection_in_real_logs(self, tmp_path):
+        """Test error detection in realistic log scenarios."""
+        log_content = """{"timestamp": "2024-01-15T10:30:00Z", "level": "INFO", "message": "Application started"}
+{"timestamp": "2024-01-15T10:30:01Z", "level": "ERROR", "message": "Traceback (most recent call last):"}
+{"timestamp": "2024-01-15T10:30:02Z", "level": "ERROR", "message": "KeyError: 'user_id'"}
+{"timestamp": "2024-01-15T10:30:03Z", "level": "INFO", "message": "Recovery successful"}
+"""
+        log_file = tmp_path / "errors.log"
+        log_file.write_text(log_content)
+
+        analyzer = LogAnalyzer()
+        result = analyzer.analyze_file(str(log_file))
+
+        assert result.error_count == 2
+        assert len(result.top_errors) > 0
+
+    def test_mixed_format_detection(self, tmp_path):
+        """Test auto-detection with different log formats."""
+        log_content = """{"level": "INFO", "message": "JSON log entry"}
+{"level": "ERROR", "message": "JSON error entry"}
+"""
+        log_file = tmp_path / "mixed.log"
+        log_file.write_text(log_content)
+
+        analyzer = LogAnalyzer()
+        result = analyzer.analyze_file(str(log_file))
+
+        assert result.parsed_count == 2
+
+    def test_large_file_handling(self, tmp_path):
+        """Test handling of larger log files."""
+        lines = []
+        for i in range(1000):
+            if i % 10 == 0:
+                lines.append(f'{{"level": "ERROR", "message": "Error at line {i}"}}')
+            else:
+                lines.append(f'{{"level": "INFO", "message": "Line {i}"}}')
+
+        log_file = tmp_path / "large.log"
+        log_file.write_text("\n".join(lines))
+
+        analyzer = LogAnalyzer()
+        result = analyzer.analyze_file(str(log_file))
+
+        assert result.total_lines == 1000
+        assert result.error_count == 100