src/main/java/org/fest/assertions/Assert.java
protected final void fail(@NotNull String reason, @Nullable Throwable cause) {
    Fail.fail(formattedErrorMessage(reason), cause);
  }
protected final void fail(@NotNull String reason, @Nullable Throwable cause) {
    Fail.fail(formattedErrorMessage(reason), cause);
  }
Fails by throwing an {@code AssertionError}.

@param reason the reason for the failure, used as the message for the thrown exception.
@param cause  the root cause of the failure, included in the thrown exception.
@throws NullPointerException if the given reason is {@code null}.