public void GetFileContents_ThrowsExcption_WhenFileContentsEmpty()
{
// Arrange
var filePath = fixture.Create <string>();
var fileContents = string.Empty;
var expectedMessage = "LISP file cannot be empty.";
_fileServiceMock.Setup(s => s.GetContents(It.IsAny <string>())).ReturnsAsync(fileContents);
// Act
// Assert
var exception = Assert.ThrowsAsync <ArgumentException>(() => _sut.GetFileContents(filePath));
Assert.AreEqual(expectedMessage, exception.Message);
}