refactor: add integration test suite

build.zig

@@ -40,7 +40,19 @@ pub fn build(b: *std.Build) void {
     });
     const run_exe_tests = b.addRunArtifact(exe_tests);
 
+    // Integration test suite: exercises the public API by performing real
+    // filesystem operations and verifying Handler callbacks via TestHandler.
+    const integration_tests = b.addTest(.{
+        .root_module = b.createModule(.{
+            .root_source_file = b.path("src/nightwatch_test.zig"),
+            .target = target,
+            .optimize = optimize,
+        }),
+    });
+    const run_integration_tests = b.addRunArtifact(integration_tests);
+
     const test_step = b.step("test", "Run tests");
     test_step.dependOn(&run_mod_tests.step);
     test_step.dependOn(&run_exe_tests.step);
+    test_step.dependOn(&run_integration_tests.step);
 }