[java] How to test that no exception is thrown?

You can create any kind of your own assertions based on assertions from junit:

static void assertDoesNotThrow(Executable executable) {
    assertDoesNotThrow(executable, "must not throw");
}
static void assertDoesNotThrow(Executable executable, String message) {
    try {
        executable.execute();
    } catch (Throwable err) {
        fail(message);
    }
}

And test:

//the following will succeed
assertDoesNotThrow(()->methodMustNotThrow(1));
assertDoesNotThrow(()->methodMustNotThrow(1), "fail with specific message: facepalm");
//the following will fail
assertDoesNotThrow(()->methodMustNotThrow(2));
assertDoesNotThrow(()-> {throw new Exception("Hello world");}, "Fail: must not trow");

Generally speaking there is possibility to instantly fail("bla bla bla") the test in any scenarios, in any place where it makes sense. For instance use it in a try/catch block to fail if anything is thrown in the test case:

try{methodMustNotThrow(1);}catch(Throwable e){fail("must not throw");}
//or
try{methodMustNotThrow(1);}catch(Throwable e){Assertions.fail("must not throw");}

This is the sample of the method we test, supposing we have such a method that must not fail under specific circumstances, but it can fail:

void methodMustNotThrow(int x) throws Exception{
    if (x == 1) return;
    throw new Exception();
}

The above method is a simple sample. But this works for complex situations, where the failure is not so obvious. There are the imports:

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.function.Executable;
import static org.junit.jupiter.api.Assertions.*;

Examples related to java

Under what circumstances can I call findViewById with an Options Menu / Action Bar item? How much should a function trust another function How to implement a simple scenario the OO way Two constructors How do I get some variable from another class in Java? this in equals method How to split a string in two and store it in a field How to do perspective fixing? String index out of range: 4 My eclipse won't open, i download the bundle pack it keeps saying error log

Examples related to unit-testing

Deprecated Gradle features were used in this build, making it incompatible with Gradle 5.0 How to test the type of a thrown exception in Jest Unit Tests not discovered in Visual Studio 2017 Class Not Found: Empty Test Suite in IntelliJ Angular 2 Unit Tests: Cannot find name 'describe' Enzyme - How to access and set <input> value? Mocking HttpClient in unit tests Example of Mockito's argumentCaptor How to write unit testing for Angular / TypeScript for private methods with Jasmine Why is the Visual Studio 2015/2017/2019 Test Runner not discovering my xUnit v2 tests

Examples related to exception

Connection Java-MySql : Public Key Retrieval is not allowed How to print an exception in Python 3? ASP.NET Core Web API exception handling Catching FULL exception message How to get exception message in Python properly What does "Fatal error: Unexpectedly found nil while unwrapping an Optional value" mean? what does Error "Thread 1:EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)" mean? Argument Exception "Item with Same Key has already been added" The given key was not present in the dictionary. Which key? sql try/catch rollback/commit - preventing erroneous commit after rollback

Examples related to junit

Eclipse No tests found using JUnit 5 caused by NoClassDefFoundError for LauncherFactory How to resolve Unneccessary Stubbing exception JUnit 5: How to assert an exception is thrown? How do I mock a REST template exchange? Class Not Found: Empty Test Suite in IntelliJ Unable to find a @SpringBootConfiguration when doing a JpaTest Failed to load ApplicationContext (with annotation) Example of Mockito's argumentCaptor Mockito - NullpointerException when stubbing Method Spring jUnit Testing properties file

Examples related to junit4

Mockito: Mock private field initialization java.lang.Exception: No runnable methods exception in running JUnits How to write JUnit test with Spring Autowire? How to run JUnit tests with Gradle? Difference between @Before, @BeforeClass, @BeforeEach and @BeforeAll How to test that no exception is thrown? Failed to load ApplicationContext for JUnit test of Spring controller How does Junit @Rule work? maven error: package org.junit does not exist How do I assert an Iterable contains elements with a certain property?