Fix an error handling for config set command (#70)

cmd/config/set.go

@@ -46,13 +46,9 @@ Can set the below settings:
 			err = entry.Set(key, value)
 			if err != nil {
 				if isInvalidKeyError(err) {
-					err := cmd.Help()
-					if err != nil {
-						return err
-					}
-				} else {
-					return err
+					_ = cmd.Help()
 				}
+				return err
 			}
 
 			err = config.Save()

cmd/config/set_test.go

@@ -27,26 +27,27 @@ func TestConfigSetCmd(t *testing.T) {
 	testCase := []struct {
 		name     string
 		args     []string
-		wantOut  string
-		checkErr bool
+		existErr bool
 	}{
 		{
 			name:     "success",
 			args:     []string{"set", "api-url", "example.com"},
-			wantOut:  "",
-			checkErr: false,
+			existErr: false,
 		},
 		{
 			name:     "failure by too many args",
 			args:     []string{"set", "api-url", "example.com", "many"},
-			wantOut:  "",
-			checkErr: true,
+			existErr: true,
 		},
 		{
 			name:     "failure by too little args",
 			args:     []string{"set", "api-url"},
-			wantOut:  "",
-			checkErr: true,
+			existErr: true,
+		},
+		{
+			name:     "failure by setting an invalid key",
+			args:     []string{"set", "invalid-key", "invalid-value"},
+			existErr: true,
 		},
 	}
 
@@ -57,13 +58,7 @@ func TestConfigSetCmd(t *testing.T) {
 			buf := bytes.NewBuffer(nil)
 			cmd.SetOut(buf)
 			err := cmd.Execute()
-			if tt.checkErr {
-				assert.NotNil(t, err)
-			} else {
-				assert.Nil(t, err)
-				assert.Equal(t, tt.wantOut, buf.String())
-			}
-
+			assert.Equal(t, tt.existErr, err != nil)
 		})
 	}
 }