Tests valid_number_step() without offset.
function testNumberStep() {
// Value and step equal.
$this
->assertTrue(valid_number_step(10.3, 10.3));
// Valid integer steps.
$this
->assertTrue(valid_number_step(42, 21));
$this
->assertTrue(valid_number_step(42, 3));
// Valid float steps.
$this
->assertTrue(valid_number_step(42, 10.5));
$this
->assertTrue(valid_number_step(1, 1 / 3));
$this
->assertTrue(valid_number_step(-100, 100 / 7));
$this
->assertTrue(valid_number_step(1000, -10));
// Valid and very small float steps.
$this
->assertTrue(valid_number_step(1000.12345, 1.0E-10));
$this
->assertTrue(valid_number_step(3.9999999999999, 1.0E-13));
// Invalid integer steps.
$this
->assertFalse(valid_number_step(100, 30));
$this
->assertFalse(valid_number_step(-10, 4));
// Invalid float steps.
$this
->assertFalse(valid_number_step(6, 5 / 7));
$this
->assertFalse(valid_number_step(10.3, 10.25));
// Step mismatches very close to beeing valid.
$this
->assertFalse(valid_number_step(70 + 9.0E-7, 10 + 9.0E-7));
$this
->assertFalse(valid_number_step(1936.5, 3.0E-8));
}