Assert with Grace: Custom Soft Assertions using AssertJ for Cleaner Code

Introduction

If you don’t know what a soft assertion is, please read which shows you how to create custom assertions using AssertJ. Here you will learn how to extend its approach to use the soft assertion approach on top of the custom assertion.

Custom Soft Assertions with AssertJ

You can have a hard assertion using the Assertions class from AssertJ or a custom one. To get all the benefits of the soft assertion we need to:

• have a custom assertion implemented


• create the custom soft assertion class and extend the AbstractSoftAssertions from AssertJ

The custom assertion

You learned how to create a custom assertion in the class is responsible for the soft assertions. This is the example applicable to the Simulation context:

@Test

public void normalSoftAssertion() {

    SoftAssertions.assertSoftly(softly -> {

        var simulation = Simulation.builder().name("John").cpf("9582728395").email("[email protected]")

                .amount(new BigDecimal("500")).installments(1).insurance(false).build();

        softly.assertThat(simulation.getInstallments()).isEqualTo(1);

        softly.assertThat(simulation.getAmount()).isEqualTo(500);

    });

}

The “problem” using it is that we won’t be able to use the custom assertion we have created. In the example above you can see the assertions in the installments and amount using the isEqualTo() as the SoftAssertions class has no access to the custom assertion.

We have solved this problem by creating the custom soft assertions class. So, instead of using the SoftAssertions class we will use the custom one: SimulationSoftAssert.

@Test

void simulationValidationErrorSoftAssertion() {

    var simulation = Simulation.builder().name("John").cpf("9582728395").email("[email protected]")

            .amount(new BigDecimal("500")).installments(1).insurance(false).build();

    SimulationSoftAssert.assertSoftly(softly -> {

        softly.assertThat(simulation).hasValidInstallments();

        softly.assertThat(simulation).hasValidAmount();

    });

}

The SimulationSoftAssert.assertSoftly() is a provider for the soft assertion that will call all internal methods to be able to manage the errors and other activities during the assertions. The assertThat() in use, inside the assertSoftly() will be the custom one which will have access to the custom assertion by the proxy() between the soft assert and the subject of the assertion.

Using this approach we have the custom assertions available in the soft assertion by the implementation of a custom one.

The end

That’s all folks!

You can find a fully implemented and working example in the class