denisvmedia · December 6, 2021 09:06 · Dec 6, 2021 · Dec 3, 2021 · Dec 3, 2021 · Dec 3, 2021
diff --git a/mult.go → math.go b/mult.go → math.go
@@ -1,13 +1,15 @@
-package mult
+package math
 
 import "errors"
 
 var ErrCantDivideByZero = errors.New("can't divide by zero")
 
+// divide cannot be tested directly
 func divide(x, y float32) float32 {
 	return x / y
 }
 
+// Divide is exported and will be tested
 func Divide(x, y int) (int, error) {
 	if y == 0 {
 		return 0, ErrCantDivideByZero

diff --git a/mult_test.go → math_test.go b/mult_test.go → math_test.go
@@ -1,11 +1,11 @@
-package mult_test
+package math_test // _test suffix is used to prevent private members direct tests
 
 import (
 	"log"
 	"os"
 	"testing"
 
-	. "kasten.io/k10/mult" // dot import to use public symbols without a package name
+	. "mynamespace/math" // dot import to use public symbols without a package name
 )
 
 func TestDivide(t *testing.T) {
@@ -59,6 +59,7 @@ func TestDivide(t *testing.T) {
 	}
 }
 
+// inits tests globally (package wide)
 func TestMain(m *testing.M) {
 	log.Print("setup all")
 	code := m.Run()

diff --git a/mult_test.go b/mult_test.go
@@ -50,10 +50,10 @@ func TestDivide(t *testing.T) {
 
 			res, err := Divide(tc.x, tc.y)
 			if err != tc.err {
-				t.Errorf("error expected %v", tc.err)
+				t.Errorf("error expected %v, got %v", tc.err, err)
 			}
 			if res != tc.res {
-				t.Errorf("expected %d, got %d", tc.res, res)
+				t.Errorf("result expected %d, got %d", tc.res, res)
 			}
 		})
 	}

diff --git a/mult.go b/mult.go
@@ -1,12 +1,16 @@
 package mult
 
+import "errors"
+
+var ErrCantDivideByZero = errors.New("can't divide by zero")
+
 func divide(x, y float32) float32 {
-	if y == 0 {
-		panic("can't divide by zero") // otherise it returns +/-Inf
-	}
 	return x / y
 }
 
-func Divide(x, y int) int {
-	return int(divide(float32(x), float32(y)))
+func Divide(x, y int) (int, error) {
+	if y == 0 {
+		return 0, ErrCantDivideByZero
+	}
+	return int(divide(float32(x), float32(y))), nil
 }
diff --git a/mult.go b/mult.go
@@ -0,0 +1,12 @@
+package mult
+
+func divide(x, y float32) float32 {
+	if y == 0 {
+		panic("can't divide by zero") // otherise it returns +/-Inf
+	}
+	return x / y
+}
+
+func Divide(x, y int) int {
+	return int(divide(float32(x), float32(y)))
+}
diff --git a/mult_test.go b/mult_test.go
@@ -0,0 +1,67 @@
+package mult_test
+
+import (
+	"log"
+	"os"
+	"testing"
+
+	. "kasten.io/k10/mult" // dot import to use public symbols without a package name
+)
+
+func TestDivide(t *testing.T) {
+	cases := []struct {
+		name string
+		x    int
+		y    int
+		res  int
+		err  error
+	}{
+		{
+			name: "integer dividable without reminder",
+			x:    4,
+			y:    2,
+			res:  2,
+		},
+		{
+			name: "integer dividable with reminder",
+			x:    3,
+			y:    2,
+			res:  1,
+		},
+		{
+			name: "divide by zero",
+			x:    4,
+			y:    0,
+			err:  ErrCantDivideByZero,
+		},
+		{
+			name: "Intentionally broken test case",
+			x:    0,
+			y:    0,
+			res:  1,
+			err:  nil,
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			log.Print("before test")
+			defer log.Print("after test")
+
+			res, err := Divide(tc.x, tc.y)
+			if err != tc.err {
+				t.Errorf("error expected %v", tc.err)
+			}
+			if res != tc.res {
+				t.Errorf("expected %d, got %d", tc.res, res)
+			}
+		})
+	}
+}
+
+func TestMain(m *testing.M) {
+	log.Print("setup all")
+	code := m.Run()
+	log.Print("teardown all")
+	os.Exit(code)
+}