Added tests for login functionality

Author: dmakarau

Tests/HabitTrackerAppServerTests/HabitTrackerAppServerLoginTests.swift

@@ -83,6 +83,28 @@ struct HabitTrackerAppServerLoginTests {
             }
         }
     }
+    
+    @Test("Test User Login Fail - Wrong username and wrong password")
+    func testUserLoginFailureWrongUsernameAndWrongPassword() async throws {
+        try await withApp(configure: configure) { app in
+            // Create user in this app instance
+            try await createUser(in: app)
+
+            // Now test login with the same app instance
+            let loginCredentials = User(username: "wronguser", password: "wrongpassword")
+            try await app.testing().test(.POST, "/api/login") { req in
+                try req.content.encode(loginCredentials)
+            } afterResponse: { res in
+                #expect(res.status == .badRequest)
+                // Check that we get a meaningful error response (not empty)
+                #expect(!res.body.string.isEmpty)
+                #expect(res.body.string.contains("User not found"))
+
+            }
+        }
+    }
+    
+    
 }