Minor fix to stringvalidator.LengthBetween() (#157)

* Minor fix to `LengthBetween()`

The Go doc comment now more accurately reflects the validator behavior.

An unnecessary validation (max cannot be less than zero) was removed.

* add test cases for `stringvalidator.LengthBetween`'s inclusive behavior

* Update stringvalidator/length_between_test.go

Suggested change from @bendbennett

Co-authored-by: Benjamin Bennett <[email protected]>

* Update stringvalidator/length_between_test.go

Suggested change from @bendbennett

Co-authored-by: Benjamin Bennett <[email protected]>

---------

Co-authored-by: Benjamin Bennett <[email protected]>

Author: chrismarget

stringvalidator/length_between.go

@@ -47,14 +47,14 @@ func (v lengthBetweenValidator) ValidateString(ctx context.Context, request vali
 	}
 }
 
-// LengthBetween returns an validator which ensures that any configured
-// attribute value is of single-byte character length greater than the given
-// minimum and less than the given maximum. Null (unconfigured) and unknown
-// (known after apply) values are skipped.
+// LengthBetween returns a validator which ensures that any configured
+// attribute value is of single-byte character length greater than or equal
+// to the given minimum and less than or equal to the given maximum. Null
+// (unconfigured) and unknown (known after apply) values are skipped.
 //
 // Use UTF8LengthBetween for checking multiple-byte characters.
 func LengthBetween(minLength, maxLength int) validator.String {
-	if minLength < 0 || maxLength < 0 || minLength > maxLength {
+	if minLength < 0 || minLength > maxLength {
 		return nil
 	}
 

stringvalidator/length_between_test.go

@@ -39,6 +39,26 @@ func TestLengthBetweenValidator(t *testing.T) {
 			minLength: 1,
 			maxLength: 3,
 		},
+		"valid minimum": {
+			val:       types.StringValue("ok"),
+			minLength: 2,
+			maxLength: 3,
+		},
+		"valid maximum": {
+			val:       types.StringValue("ok"),
+			minLength: 1,
+			maxLength: 2,
+		},
+		"valid minimum maximum equal": {
+			val:       types.StringValue("ok"),
+			minLength: 2,
+			maxLength: 2,
+		},
+		"valid minimum maximum zero": {
+			val:       types.StringValue(""),
+			minLength: 0,
+			maxLength: 0,
+		},
 		"too long": {
 			val:         types.StringValue("not ok"),
 			minLength:   1,