Function handler

test/runTest/client/client.js:429–443

(newVal, oldVal)

        'runConfig.expectedSource': {
            handler(newVal, oldVal) {
                if (newVal === oldVal) {
                    return;
                }

                handlingSourceChange = true;
                this.$nextTick(() => {
                    this.runConfig.expectedVersion = getVersionFromSource(
                        newVal,
                        this.versions,
                        this.nightlyVersions
                    );
                    handlingSourceChange = false;
                });
            },
            deep: false
        },