Why is this an issue?

Using literal boolean values in assertions can lead to less readable and less informative unit tests. When a test fails, it’s important to have a clear understanding of what the test was checking and why it failed. Most of the testing frameworks provide more explicit assertion methods that will provide a more helpful error message if the test fails.

Exceptions

In the context of xUnit, Assert.True and Assert.False are not flagged by this rule. This is because Assert.Fail was only introduced in 2020 with version 2.4.2. Prior to this, developers used Assert.True(false, message) and Assert.False(true, message) as workarounds to simulate the functionality of Assert.Fail().

How to fix it in MSTest

Code examples

Noncompliant code example

bool someResult;

Assert.AreEqual(false, someResult); // Noncompliant: use Assert.IsFalse
Assert.AreEqual(true, someResult); // Noncompliant: use Assert.IsTrue
Assert.AreNotEqual(false, someResult); // Noncompliant: use Assert.IsTrue
Assert.AreNotEqual(true, someResult); // Noncompliant: use Assert.IsFalse
Assert.IsFalse(true, "Should not reach this line!"); // Noncompliant: use Assert.Fail
Assert.IsTrue(false, "Should not reach this line!"); // Noncompliant: use Assert.Fail
Assert.IsFalse(false); // Noncompliant: remove it

Compliant solution

bool someResult;

Assert.IsFalse(someResult);
Assert.IsTrue(someResult);
Assert.IsTrue(someResult);
Assert.IsFalse(someResult);
Assert.Fail("Should not reach this line!");
Assert.Fail("Should not reach this line!");
// Removed

How to fix it in NUnit

Code examples

Noncompliant code example

bool someResult;

Assert.AreEqual(false, someResult); // Noncompliant: use Assert.False
Assert.AreEqual(true, someResult); // Noncompliant: use Assert.True
Assert.AreNotEqual(false, someResult); // Noncompliant: use Assert.True
Assert.AreNotEqual(true, someResult); // Noncompliant: use Assert.False
Assert.False(true, "Should not reach this line!"); // Noncompliant: use Assert.Fail
Assert.True(false, "Should not reach this line!"); // Noncompliant: use Assert.Fail
Assert.False(false); // Noncompliant: remove it

Compliant solution

bool someResult;

Assert.False(someResult);
Assert.True(someResult);
Assert.True(someResult);
Assert.False(someResult);
Assert.Fail("Should not reach this line!");
Assert.Fail("Should not reach this line!");
// Removed

How to fix it in xUnit

Code examples

Noncompliant code example

bool someResult;

Assert.Equal(false, someResult); // Noncompliant: use Assert.False
Assert.Equal(true, someResult); // Noncompliant: use Assert.True
Assert.NotEqual(false, someResult); // Noncompliant: use Assert.True
Assert.NotEqual(true, someResult); // Noncompliant: use Assert.False

Compliant solution

bool someResult;

Assert.False(someResult);
Assert.True(someResult);
Assert.True(someResult);
Assert.False(someResult);

Resources

Documentation