public void AmountErasedShouldNotExceedEraserDurability(int wordLength) { var sut = new Pencil(); var word = new string('a', wordLength); var result = sut.BuildWordForErasing(word); int whiteSpaceCount = 0; foreach (var letter in result) { if (letter == ' ') { whiteSpaceCount++; } } Assert.True(20000 >= whiteSpaceCount); }