MockMvc for HTTP assertions in Spring Boot - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is MockMvc in Spring Boot testing?

MockMvc is a tool in Spring Boot that lets you test your web controllers by simulating HTTP requests and responses without starting a real server.

beginner

How do you perform a GET request using MockMvc?

You use mockMvc.perform(get("/your-url")) to simulate a GET request to the specified URL.

beginner

What method do you use to check the HTTP status in MockMvc assertions?

You use andExpect(status().isOk()) to check if the HTTP response status is 200 OK.

intermediate

How can you verify the response content type with MockMvc?

Use andExpect(content().contentType("application/json")) to check if the response content type is JSON.

intermediate

Why is MockMvc useful compared to starting a full server for tests?

MockMvc runs tests faster and isolates controller logic by simulating HTTP calls without starting the full web server, making tests quicker and easier to run.

Which MockMvc method simulates an HTTP POST request?

A delete("/url")

B get("/url")

C put("/url")

D post("/url")

The post() method simulates an HTTP POST request in MockMvc.

How do you check if the response status is 404 Not Found in MockMvc?

A andExpect(status().isBadRequest())

B andExpect(status().isNotFound())

C andExpect(status().isOk())

D andExpect(status().isUnauthorized())

Use status().isNotFound() to assert a 404 HTTP status.

What does mockMvc.perform() return?

A The full HTTP request object

B The HTTP response body as a string

C A ResultActions object to chain assertions

D A boolean indicating success

mockMvc.perform() returns a ResultActions object that allows chaining assertions like status and content checks.

Which annotation is commonly used to inject MockMvc in Spring Boot tests?

A @AutoConfigureMockMvc

B @MockBean

C @SpringBootApplication

D @Controller

@AutoConfigureMockMvc sets up MockMvc for testing in Spring Boot.

How do you verify JSON content in the response using MockMvc?

A andExpect(content().json("{\"key\":\"value\"}"))

B andExpect(content().string("value"))

C andExpect(jsonPath("$.key").exists())

D andExpect(status().isJson())

Use content().json() to check if the response JSON matches the expected string.

Explain how MockMvc helps test Spring Boot controllers without starting a server.

Think about how you can test web calls without opening a browser or server.

Describe the steps to write a MockMvc test that checks a GET request returns status 200 and JSON content.

Start with performing the request, then add assertions.

Practice

1. What is the main purpose of using MockMvc in Spring Boot tests?

easy

A. To test HTTP requests and responses without starting a real server

B. To deploy the application to a production server

C. To generate HTML pages automatically

D. To manage database connections

Solution

1. Step 1: Understand MockMvc role

   MockMvc simulates HTTP requests and responses in tests without needing a real server.

2. Step 2: Compare options

   Options A, B, and D describe unrelated tasks like HTML generation, deployment, or database management.

3. Final Answer:

   To test HTTP requests and responses without starting a real server -> Option A

4. Quick Check:

   MockMvc = HTTP testing without server [OK]

Hint: MockMvc tests HTTP calls without running the server [OK]

Common Mistakes:

• Thinking MockMvc starts a real server
• Confusing MockMvc with deployment tools
• Assuming MockMvc manages databases

2. Which of the following is the correct way to perform a GET request using MockMvc?

easy

A. mockMvc.perform(get("/api/data"))

B. mockMvc.get("/api/data")

C. mockMvc.request("GET", "/api/data")

D. mockMvc.callGet("/api/data")

Solution

1. Step 1: Recall MockMvc syntax

   The correct syntax uses mockMvc.perform(get("/url")) with static import of get.

2. Step 2: Check other options

   Options B, C, and D use invalid method names not provided by MockMvc API.

3. Final Answer:

   mockMvc.perform(get("/api/data")) -> Option A

4. Quick Check:

   Use perform(get()) for GET requests [OK]

Hint: Use perform(get("url")) to send GET requests [OK]

Common Mistakes:

• Using mockMvc.get() directly
• Confusing method names like request() or callGet()
• Not importing static get() method

3. Given the following test snippet, what HTTP status code will be asserted?

mockMvc.perform(get("/hello"))
       .andExpect(status().isOk());

medium

A. 404 Not Found

B. 500 Internal Server Error

C. 200 OK

D. 302 Redirect

Solution

1. Step 1: Understand status().isOk()

   The method status().isOk() checks for HTTP status code 200.

2. Step 2: Match status codes

   200 means success, 404 means not found, 500 means server error, 302 means redirect.

3. Final Answer:

   200 OK -> Option C

4. Quick Check:

   status().isOk() = 200 OK [OK]

Hint: isOk() always means HTTP 200 success [OK]

Common Mistakes:

• Confusing isOk() with error codes
• Assuming isOk() means redirect
• Mixing status codes meanings

4. Identify the error in this MockMvc test code snippet:

mockMvc.perform(post("/submit"))
       .andExpect(status().isOk)
       .andExpect(content().string("Success"));

medium

A. Using post instead of get for /submit

B. Missing parentheses after isOk method call

C. Incorrect content matcher method name

D. No error, code is correct

Solution

1. Step 1: Check method calls

   The method isOk must be called with parentheses: isOk().

2. Step 2: Verify other parts

   Using post for /submit is valid; content().string() is correct; so no other errors.

3. Final Answer:

   Missing parentheses after isOk method call -> Option B

4. Quick Check:

   Method calls need parentheses like isOk() [OK]

Hint: Always add () after status check methods like isOk() [OK]

Common Mistakes:

• Forgetting parentheses on isOk()
• Confusing post and get methods
• Using wrong content matcher method

5. You want to test a JSON response from /user/1 endpoint that returns {"name":"Alice","age":30}. Which MockMvc assertion correctly checks the name field in the JSON response?

hard

A. andExpect(content().string("Alice"))

B. andExpect(content().json("name: Alice"))

C. andExpect(jsonPath("name").isEqualTo("Alice"))

D. andExpect(jsonPath("$.name").value("Alice"))

Solution

1. Step 1: Understand JSON path syntax

   To check JSON fields, use jsonPath("$.fieldName") with value() for expected value.

2. Step 2: Evaluate options

   andExpect(jsonPath("$.name").value("Alice")) uses correct syntax. andExpect(content().json("name: Alice")) has invalid JSON format. andExpect(jsonPath("name").isEqualTo("Alice")) uses wrong jsonPath syntax. andExpect(content().string("Alice")) checks whole string, not JSON field.

3. Final Answer:

   andExpect(jsonPath("$.name").value("Alice")) -> Option D

4. Quick Check:

   Use jsonPath("$.field").value() for JSON checks [OK]

Hint: Use jsonPath("$.field").value(expected) to check JSON fields [OK]

Common Mistakes:

• Wrong jsonPath syntax without $
• Trying to match JSON with plain string
• Using incorrect matcher methods