src/main/java/org/fest/assertions/internal/Doubles.java
public void assertIsNaN(Description description, Double actual) {
    comparables.assertEqual(description, actual, NaN);
  }
public void assertIsNaN(Description description, Double actual) {
    comparables.assertEqual(description, actual, NaN);
  }
Verifies that the actual value is equal to {@code NaN}.

@param description the description of the <em>actual</em> value.
@param actual the <em>actual</em> value.