add test to validation function

go/vt/mysqlctl/xtrabackupengine_test.go

@@ -18,8 +18,10 @@ package mysqlctl
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"math/rand"
+	"strings"
 	"testing"
 
 	"vitess.io/vitess/go/vt/logutil"
@@ -115,3 +117,40 @@ func TestStripeRoundTrip(t *testing.T) {
 	// Test block size and stripe count that don't evenly divide data size.
 	test(6000, 7)
 }
+
+func TestValidateExternalDecompressor(t *testing.T) {
+	tests := []struct {
+		cmdName string
+		path    string
+		errStr  string
+	}{
+		// this should not find an executable
+		{"non_existent_cmd", "", "executable file not found"},
+		// we expect ls to be on PATH as it is a basic command part of busybox and most containers
+		{"ls", "ls", ""},
+	}
+
+	for i, tt := range tests {
+		t.Run(fmt.Sprintf("Test #%d", i+1), func(t *testing.T) {
+			CmdName := tt.cmdName
+
+			path, err := validateExternalDecompressor(CmdName)
+
+			if tt.path != "" {
+				if !strings.HasSuffix(path, tt.path) {
+					t.Errorf("Expected path \"%s\" to include \"%s\"", path, tt.path)
+				}
+			}
+
+			if tt.errStr == "" {
+				if err != nil {
+					t.Errorf("Expected result \"%v\", got \"%v\"", "<nil>", err)
+				}
+			} else {
+				if !strings.Contains(fmt.Sprintf("%v", err), tt.errStr) {
+					t.Errorf("Expected result \"%v\", got \"%v\"", tt.errStr, err)
+				}
+			}
+		})
+	}
+}