improve validate testing with examples

also simplified structure of test cases and failure logging

length_test.go

@@ -2,57 +2,60 @@ package validate
 
 import (
 	"errors"
+	"fmt"
 	"testing"
 )
 
+func ExampleMaxLength() {
+	testMaxLength := MaxLength(8)
+	fmt.Println(testMaxLength("this string is too long"))
+	// Output: must contain no more than 8 characters
+}
+
+func ExampleMinLength() {
+	testMinLength := MinLength(8)
+	fmt.Println(testMinLength("2short"))
+	// Output: must contain at least 8 characters
+}
+
 func TestMaxLength(t *testing.T) {
-	type TestCase struct {
-		Input string
-		L     int
-		Err   error
+	testCases := map[int]map[string]error{
+		8: {"abcd": nil, "abcdefgh": nil, "abcd efg": nil, "abcdefghi": ErrMustBeShorter.With(8)},
 	}
 
-	testCases := []TestCase{
-		{Input: "abcd", L: 8},
-		{Input: "abcdefgh", L: 8},
-		{Input: "abcd efg", L: 8},
-		{Input: "abcdefghi", L: 8, Err: ErrMustBeShorter},
-	}
+	for setup, values := range testCases {
+		testMaxLength := MaxLength(setup)
 
-	for n, tc := range testCases {
-		t.Logf("(%d) Testing %q against maximum length of %d", n, tc.Input, tc.L)
+		for input, want := range values {
+			t.Run(fmt.Sprintf("%d/%s", setup, input), func(t *testing.T) {
+				got := testMaxLength(input)
 
-		f := MaxLength(tc.L)
-		err := f(tc.Input)
-
-		if !errors.Is(err, tc.Err) {
-			t.Errorf("Expected error %v, got %v", tc.Err, err)
+				if !errors.Is(got, want) {
+					t.Error("got", got)
+					t.Error("want", want)
+				}
+			})
 		}
 	}
 }
 
 func TestMinLength(t *testing.T) {
-	type TestCase struct {
-		Input string
-		L     int
-		Err   error
+	testCases := map[int]map[string]error{
+		8: {"abcd": ErrMustBeLonger.With(8), "abcdefgh": nil, "abcd efg": nil, "abcdefghi": nil},
 	}
 
-	testCases := []TestCase{
-		{Input: "abcd", L: 8, Err: ErrMustBeLonger},
-		{Input: "abcdefgh", L: 8},
-		{Input: "abcd efg", L: 8},
-		{Input: "abcdefghi", L: 8},
-	}
+	for setup, values := range testCases {
+		testMinLength := MinLength(setup)
 
-	for n, tc := range testCases {
-		t.Logf("(%d) Testing %q against minimum length of %d", n, tc.Input, tc.L)
+		for input, want := range values {
+			t.Run(fmt.Sprintf("%d/%s", setup, input), func(t *testing.T) {
+				got := testMinLength(input)
 
-		f := MinLength(tc.L)
-		err := f(tc.Input)
-
-		if !errors.Is(err, tc.Err) {
-			t.Errorf("Expected error %v, got %v", tc.Err, err)
+				if !errors.Is(got, want) {
+					t.Error("got", got)
+					t.Error("want", want)
+				}
+			})
 		}
 	}
 }