src/main/java/org/fest/assertions/ThrowableAssert.java
public @NotNull ThrowableAssert hasMessage(@Nullable String message) {
    isNotNull();
    failIfNotEqual(customErrorMessage(), rawDescription(), actual.getMessage(), message);
    return this;
  }
public @NotNull ThrowableAssert hasMessage(@Nullable String message) {
    isNotNull();
    failIfNotEqual(customErrorMessage(), rawDescription(), actual.getMessage(), message);
    return this;
  }
Verifies that the message of the actual {@code Throwable} is equal to the given one.

@param message the expected message.
@return this assertion error.
@throws AssertionError if the actual {@code Throwable} is {@code null}.
@throws AssertionError if the message of the actual {@code Throwable} is not equal to the given one.