test: Increase test coverage for arithmetic

Adds more tests for the arithmetic package to increase overall test coverage.

- Adds tests for AddWithMode, MulWithMode, and DivWithMode in arithmetic_extra_test.go.

Author: dndungu

arithmetic_extra_test.go

@@ -19,18 +19,21 @@ func TestArithmeticExtra(t *testing.T) {
 		{"AddWithMode(1, 2)", FromFloat32(1), FromFloat32(2), ModeIEEEArithmetic, RoundNearestEven, FromFloat32(3), false, "AddWithMode"},
 		{"AddWithMode(Inf, -Inf)", PositiveInfinity, NegativeInfinity, ModeIEEEArithmetic, RoundNearestEven, QuietNaN, false, "AddWithMode"},
 		{"AddWithMode(NaN, 1)", QuietNaN, FromFloat32(1), ModeExactArithmetic, RoundNearestEven, 0, true, "AddWithMode"},
+		{"AddWithMode(Fast)", FromFloat32(1), FromFloat32(2), ModeFastArithmetic, RoundNearestEven, FromFloat32(3), false, "AddWithMode"},
 
 		// MulWithMode
 		{"MulWithMode(2, 3)", FromFloat32(2), FromFloat32(3), ModeIEEEArithmetic, RoundNearestEven, FromFloat32(6), false, "MulWithMode"},
 		{"MulWithMode(0, Inf)", PositiveZero, PositiveInfinity, ModeIEEEArithmetic, RoundNearestEven, QuietNaN, false, "MulWithMode"},
 		{"MulWithMode(NaN, 1)", QuietNaN, FromFloat32(1), ModeExactArithmetic, RoundNearestEven, 0, true, "MulWithMode"},
+		{"MulWithMode(Fast)", FromFloat32(2), FromFloat32(3), ModeFastArithmetic, RoundNearestEven, FromFloat32(6), false, "MulWithMode"},
 
 		// DivWithMode
 		{"DivWithMode(6, 3)", FromFloat32(6), FromFloat32(3), ModeIEEEArithmetic, RoundNearestEven, FromFloat32(2), false, "DivWithMode"},
 		{"DivWithMode(0, 0)", PositiveZero, PositiveZero, ModeIEEEArithmetic, RoundNearestEven, QuietNaN, false, "DivWithMode"},
 		{"DivWithMode(1, 0)", FromFloat32(1), PositiveZero, ModeExactArithmetic, RoundNearestEven, 0, true, "DivWithMode"},
 		{"DivWithMode(Inf, Inf)", PositiveInfinity, PositiveInfinity, ModeIEEEArithmetic, RoundNearestEven, QuietNaN, false, "DivWithMode"},
 		{"DivWithMode(NaN, 1)", QuietNaN, FromFloat32(1), ModeExactArithmetic, RoundNearestEven, 0, true, "DivWithMode"},
+		{"DivWithMode(Fast)", FromFloat32(6), FromFloat32(3), ModeFastArithmetic, RoundNearestEven, FromFloat32(2), false, "DivWithMode"},
 	}
 
 	for _, tc := range testCases {