public void IsValidWithNoArgumentTests()
{
var attribute = new FileExtensionsAttribute();
Assert.IsTrue(attribute.IsValid(null)); // Optional values are always valid
Assert.IsTrue(attribute.IsValid("foo.png"));
Assert.IsTrue(attribute.IsValid("foo.jpeg"));
Assert.IsTrue(attribute.IsValid("foo.jpg"));
Assert.IsTrue(attribute.IsValid("foo.gif"));
Assert.IsTrue(attribute.IsValid(@"C:\Foo\bar.png"));
Assert.IsFalse(attribute.IsValid("foo"));
Assert.IsFalse(attribute.IsValid("foo.doc"));
Assert.IsFalse(attribute.IsValid("foo.txt"));
Assert.IsFalse(attribute.IsValid("foo.png.txt"));
}