How can I assert that a block of code doesn’t throw any exceptions using AssertJ?

General Discussions
1

I’m trying to write tests where I just want to make sure that some code executes without throwing exceptions. For example:

SomeService service = new SomeService();
service.doSomething();

I’d like to use AssertJ’s fluent assertions to check that no exception is thrown, something like:

// pseudo-code idea
assertThatNoException().isThrownBy(() -> service.doSomething());

Is there a recommended way in AssertJ to do this? Can I also chain it with other assertions for better fluency?

2

In my tests, I often use assertThatCode when I just want to ensure that a method doesn’t throw anything:

SomeService service = new SomeService();

assertThatCode(() -> service.doSomething())
    .doesNotThrowAnyException();

It’s straightforward and part of AssertJ’s fluent API. I like it because it reads almost like plain English.

3

Sometimes I want to assert no exception and check the return value or state change.

For example:

SomeService service = new SomeService();

assertThatCode(() -> {
        service.doSomething();
        // you can include additional assertions here
        assertThat(service.getStatus()).isEqualTo("DONE");
    })
    .doesNotThrowAnyException();

I use this pattern when I want a single, fluent block to validate behavior and exceptions at the same time.

4

If you need to inspect the exception later or log it for debugging, I sometimes do:

Throwable thrown = catchThrowable(() -> service.doSomething());

assertThat(thrown).isNull();

This approach is handy when I want a bit more control over what happens if an exception does occur, rather than just failing immediately.