Assert.Negative
Asserts that a number is negative.
//true
Assert.Negative(-1);
//false
Assert.Negative(1);
All the overloads of the method are
Assert.Negative(int actual);
Assert.Negative(int actual, string message, params object[] args);
Assert.Negative(uint actual);
Assert.Negative(uint actual, string message, params object[] args);
Assert.Negative(long actual);
Assert.Negative(long actual, string message, params object[] args);
Assert.Negative(ulong actual);
Assert.Negative(ulong actual, string message, params object[] args);
Assert.Negative(decimal actual);
Assert.Negative(decimal actual, string message, params object[] args);
Assert.Negative(double actual);
Assert.Negative(double actual, string message, params object[] args);
Assert.Negative(float actual);
Assert.Negative(float actual, string message, params object[] args);
You may also use Assert.That with a Is.Negative constraint to achieve the same result.