add min/max length validation, improve tests

length_test.go

@@ -0,0 +1,65 @@
+package validate
+
+import "testing"
+
+func TestMaxLength(t *testing.T) {
+	type TestCase struct {
+		L     int
+		Input string
+		Err   bool
+	}
+
+	testCases := []TestCase{
+		{L: 8, Input: "abcd"},
+		{L: 8, Input: "abcdefgh"},
+		{L: 8, Input: "abcd efg"},
+		{L: 8, Input: "abcdefghi", Err: true},
+	}
+
+	for _, testCase := range testCases {
+		t.Logf("Max length %d for %q", testCase.L, testCase.Input)
+
+		f := MaxLength(testCase.L)
+		err := f(testCase.Input)
+		if testCase.Err {
+			if err == nil {
+				t.Error("Expected an error; got nil")
+			}
+		} else {
+			if err != nil {
+				t.Errorf("Expected nil; got %s", err)
+			}
+		}
+	}
+}
+
+func TestMinLength(t *testing.T) {
+	type TestCase struct {
+		L     int
+		Input string
+		Err   bool
+	}
+
+	testCases := []TestCase{
+		{L: 8, Input: "abcd", Err: true},
+		{L: 8, Input: "abcdefgh"},
+		{L: 8, Input: "abcd efg"},
+		{L: 8, Input: "abcdefghi"},
+	}
+
+	for _, testCase := range testCases {
+		t.Logf("Min length %d for %q", testCase.L, testCase.Input)
+
+		f := MinLength(testCase.L)
+		err := f(testCase.Input)
+		if testCase.Err {
+			if err == nil {
+				t.Error("Expected an error; got nil")
+			}
+		} else {
+			if err != nil {
+				t.Errorf("Expected nil; got %s", err)
+			}
+		}
+	}
+}