Cannot add plugin tests of any cordova plugin

If I am trying to run the unit tests of any plugin (e.g cordova-plugin-geolocation), I have to add the tests subdirectory of the plugin in my project. While adding the tests subdirectory of a remote project, I am getting a `support for subdirectories is deprecated and will be removed in Cordova@7` error. The command I am trying to use to add the tests is 

`cordova plugin add http://git-wip-us.apache.org/repos/asf/cordova-plugin-geolocation#:/tests`.

If fetch does not support adding subdirectories, How can someone add the unit tests of a plugin in his project? The error and the stack trace is shown below:

```

(node:57857) UnhandledPromiseRejectionWarning: CordovaError: --fetch does not support subdirectories

    at Object.fetchPlugin [as fetch] (/usr/local/lib/node_modules/cordova/node_modules/cordova-lib/src/plugman/fetch.js:71:37)

    at /usr/local/lib/node_modules/cordova/node_modules/cordova-lib/src/cordova/plugin/add.js:98:40

    at _fulfilled (/usr/local/lib/node_modules/cordova/node_modules/cordova-lib/node_modules/q/q.js:787:54)

    at /usr/local/lib/node_modules/cordova/node_modules/cordova-lib/node_modules/q/q.js:816:30

    at Promise.promise.promiseDispatch (/usr/local/lib/node_modules/cordova/node_modules/cordova-lib/node_modules/q/q.js:749:13)

    at /usr/local/lib/node_modules/cordova/node_modules/cordova-lib/node_modules/q/q.js:810:14

    at flush (/usr/local/lib/node_modules/cordova/node_modules/cordova-lib/node_modules/q/q.js:108:17)

    at process._tickCallback (internal/process/next_tick.js:61:11)

    at Function.Module.runMain (internal/modules/cjs/loader.js:745:11)

    at startup (internal/bootstrap/node.js:266:19)

(node:57857) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)

(node:57857) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.```

Adding the `--nofetch` flag, does not resolve the issue either. Is cloning the project and using the location of the test directory to add to the project, the only option I have?