bcquality/microsoft/knowledge/testing/use-assert-isfalse-not-asserterror-for-boolean-checks.md

bc-version	domain	keywords	technologies	countries	application-area
all	testing	assert isfalse istrue asserterror boolean-check negative-test	al	w1	all

Use Assert.IsFalse to check a boolean result, not asserterror around Assert.IsTrue

Description

asserterror exists to assert that a statement raises a runtime error; it is not a general-purpose way to invert a boolean check. Wrapping asserterror Assert.IsTrue(SomeFunc(), Msg) to verify that SomeFunc() returns false tests whether Assert.IsTrue's own error-raising behavior fired, not the value SomeFunc() actually returned.

Best Practice

When the code under test returns a Boolean rather than raising an error, assert the value directly with Assert.IsFalse(SomeFunc(), Msg) (or Assert.IsTrue for the positive case). Reserve asserterror for statements expected to actually raise an error.

See sample: use-assert-isfalse-not-asserterror-for-boolean-checks.good.al.

Anti Pattern

asserterror Assert.IsTrue(SomeFunc(), Msg); to verify SomeFunc() is false. It passes today because Assert.IsTrue happens to raise an error on failure, but it verifies the assertion helper's error-raising behavior, not the value under test.

See sample: use-assert-isfalse-not-asserterror-for-boolean-checks.bad.al.