first commit

operator/operator.go

@@ -0,0 +1,26 @@
+package operator
+
+import "fmt"
+
+// Add returns the sum of a and b.
+func Add(a, b int) int {
+    return a + b
+}
+
+// Sub returns the difference a - b.
+func Sub(a, b int) int {
+    return a - b
+}
+
+// Mul returns the product of a and b.
+func Mul(a, b int) int {
+    return a * b
+}
+
+// Div returns the division a / b as float64. Returns an error on division by zero.
+func Div(a, b int) (float64, error) {
+    if b == 0 {
+        return 0, fmt.Errorf("divide by zero")
+    }
+    return float64(a) / float64(b), nil
+}

operator/operator_test.go

@@ -0,0 +1,41 @@
+package operator
+
+import "testing"
+
+func TestAdd(t *testing.T) {
+    got := Add(2, 3)
+    if got != 5 {
+        t.Fatalf("Add(2,3) = %d; want 5", got)
+    }
+}
+
+func TestSub(t *testing.T) {
+    got := Sub(5, 3)
+    if got != 2 {
+        t.Fatalf("Sub(5,3) = %d; want 2", got)
+    }
+}
+
+func TestMul(t *testing.T) {
+    got := Mul(4, 3)
+    if got != 12 {
+        t.Fatalf("Mul(4,3) = %d; want 12", got)
+    }
+}
+
+func TestDiv(t *testing.T) {
+    got, err := Div(7, 2)
+    if err != nil {
+        t.Fatalf("unexpected error: %v", err)
+    }
+    if got != 3.5 {
+        t.Fatalf("Div(7,2) = %v; want 3.5", got)
+    }
+}
+
+func TestDivByZero(t *testing.T) {
+    _, err := Div(1, 0)
+    if err == nil {
+        t.Fatalf("expected error when dividing by zero")
+    }
+}