How to use MatcherToString method of org.mockito.internal.matchers.text.MatcherToString class

I wonder why you want to test, what method your method under tests invoke. Sounds pretty much like whitebox testing to me.

In my opinion, you want to verify the outcome of the invocation and not the way to get there, as this might easily change (i.e. when refactoring).

So if the outcome of doSecond() is the same as doFirst() you could write a test for doFirst() and use the same test (i.e. set of assertions) for testing doSecond().

But if you really want to test, whether doFirst() has been invoked by doSecond() you could wrap your service in a spy and then call the verification on the spy:

//given
SomeService service = new SomeService();
SomeService spy = Mockito.spy(service);
//when
spy.doSecond();
//then
verify(spy).doFirst();

Not possible through mockito. From their wiki

Why Mockito doesn't mock private methods?

Firstly, we are not dogmatic about mocking private methods. We just don't care about private methods because from the standpoint of testing private methods don't exist. Here are a couple of reasons Mockito doesn't mock private methods:

It requires hacking of classloaders that is never bullet proof and it changes the api (you must use custom test runner, annotate the class, etc.).

It is very easy to work around - just change the visibility of method from private to package-protected (or protected).

It requires me to spend time implementing & maintaining it. And it does not make sense given point #2 and a fact that it is already implemented in different tool (powermock).

Finally... Mocking private methods is a hint that there is something wrong with OO understanding. In OO you want objects (or roles) to collaborate, not methods. Forget about pascal & procedural code. Think in objects.

As you pointed out, it is not possible to mock static methods with Mockito and since you do not wanna use Powermock or other tools, you can try something as follows in your tests.

1. Create test authentication object

   Authentication auth = new ... // create instance based on your needs and with required attributes or just mock it if you do not care

2. Mock security context

   SecurityContext context = mock(SecurityContext.class);

3. Ensure your mock returns the respective authentication

   when(context.getAuthentication()).thenReturn(auth);

4. Set security context into holder

   SecurityContextHolder.setContext(securityContext);

Now every call to SecurityContextHolder.getContext().getAuthentication() should return authentication object created in step 1.

I think your results are compatible with the result that would happen if dbCollection is not a Mockito-mock (or your method is static or final). That would mean that a matcher is being used where none can be used; hence the "0 matchers expected, 1 recorded".

I think you need to pass the Matcher to the jsonPath method. For example.

.andExpect(jsonPath("$.version", is("0.1")))

References:
http://docs.spring.io/spring/docs/3.2.x/javadoc-api/org/springframework/test/web/servlet/result/MockMvcResultMatchers.html#jsonPath(java.lang.String,%20org.hamcrest.Matcher)

https://www.petrikainulainen.net/programming/spring-framework/integration-testing-of-spring-mvc-applications-write-clean-assertions-with-jsonpath/

SpringMVC/ mockMVC/ jsonpath compare list of strings

I would try any(byte[].class)

The junit5-migration-gradle project demonstrates how to execute tests based on JUnit 5 using Gradle. In addition, it showcases that existing JUnit 4 based tests can be executed in the same test suite as JUnit Jupiter based tests or any other tests supported on the JUnit Platform.

Basically it boils down to having both engines, Jupiter and Vintage, on the runtime class-path:

dependencies {
    testCompile("org.junit.jupiter:junit-jupiter-api:5.2.0")
    testRuntime("org.junit.jupiter:junit-jupiter-engine:5.2.0")
}

dependencies {
    testCompile("junit:junit:4.12")
    testRuntime("org.junit.vintage:junit-vintage-engine:5.2.0")
}

Issue was due to the jar conflicts

We need to exclude

<dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
        <exclusions>
            <exclusion>
                <groupId>org.junit</groupId>
                <artifactId>junit</artifactId>
            </exclusion>
            <exclusion>
                <groupId>org.mockito</groupId>
                <artifactId>mockito-core</artifactId>
            </exclusion>
            <exclusion>
                <groupId>org.mockito</groupId>
                <artifactId>mockito-all</artifactId>
            </exclusion>
        </exclusions>
    </dependency>

And include

<dependency>
        <groupId>org.mockito</groupId>
        <artifactId>mockito-core</artifactId>
        <version>3.11.2</version>
    </dependency>

I've never used Mockito, but want to learn, so here goes. If someone less clueless than me answers, try their answer first!

Mockito.when(reader.document(anyInt())).thenAnswer(new Answer() {
 public Object answer(InvocationOnMock invocation) {
     Object[] args = invocation.getArguments();
     Object mock = invocation.getMock();
     return document(fakeIndex((int)(Integer)args[0]));
     }
 });