Test the randstr.go RandomString function

pkg/randstr/randstr.go

@@ -7,6 +7,9 @@ import (
 
 // RandomString returns a random string of a given length.
 func RandomString(length int) string {
+	if length < 0 {
+		return ""
+	}
 	charset := "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
 	randbytes := make([]byte, 0, length)
 	for i := 0; i < length; i++ {

pkg/randstr/randstr_test.go

@@ -0,0 +1,71 @@
+package randstr_test
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/ansible/receptor/pkg/randstr"
+)
+
+func TestRandStrLength(t *testing.T) {
+	randStringTestCases := []struct {
+		name           string
+		inputLength    int
+		expectedLength int
+	}{
+		{
+			name:           "length of 100",
+			inputLength:    100,
+			expectedLength: 100,
+		},
+		{
+			name:           "length of 0",
+			inputLength:    0,
+			expectedLength: 0,
+		},
+		{
+			name:           "length of -1",
+			inputLength:    -1,
+			expectedLength: 0,
+		},
+	}
+
+	for _, testCase := range randStringTestCases {
+		t.Run("Test the random string length", func(t *testing.T) {
+			randomStr := randstr.RandomString(testCase.inputLength)
+
+			if len(randomStr) != testCase.expectedLength {
+				t.Errorf("%s - expected: %+v, received: %+v", testCase.name, testCase.expectedLength, len(randomStr))
+			}
+		})
+	}
+}
+
+func TestRandStrHasDifferentOutputThanCharset(t *testing.T) {
+	charset := "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+	randomStr := randstr.RandomString(len(charset))
+
+	if randomStr == charset {
+		t.Errorf("output should be different than charset. charset: %+v, received: %+v", charset, randomStr)
+	}
+}
+
+func TestRandStrHasNoContinuousSubStringOfCharset(t *testing.T) {
+	randomStr := randstr.RandomString(10)
+	charset := "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
+
+	charsetIndex := strings.Index(charset, string(randomStr[0]))
+	for index, char := range randomStr {
+		if index == 0 {
+			continue
+		}
+		currentCharsetIndex := strings.Index(charset, string(char))
+		if charsetIndex+1 != currentCharsetIndex {
+			break
+		}
+		if index+1 == len(randomStr) {
+			t.Error("rand str is continuous")
+		}
+		charsetIndex = currentCharsetIndex
+	}
+}