public void GetEnrollmentRows_ThrowsExcption_WhenNotHeaderRow() { // Arrange var fileContents = fixture.Create <string>(); var rowSeparator = fixture.Create <char>(); var enrollmentRows = fixture.CreateMany <string>(1).ToList(); var expectedMessage = "Csv file must have more than 1 row."; _csvServiceMock.Setup(s => s.SeparateIntoRows(It.IsAny <string>(), It.IsAny <char>())).Returns(enrollmentRows); // Act // Assert var exception = Assert.Throws <ArgumentException>(() => _sut.GetEnrollmentRows(fileContents, rowSeparator)); Assert.AreEqual(expectedMessage, exception.Message); }