Docs: Updates from puppeteer to Cypress (#20962)

* Docs: Updates from puppeteer to Cypress

* e2e: Adds documentation

* Docs: Adds link to e2e framework from contributing

* Docs: Updates after PR comments

* Update contribute/style-guides/e2e.md

Co-Authored-By: Arve Knudsen <arve.knudsen@gmail.com>

* Update contribute/style-guides/e2e.md

Co-Authored-By: Arve Knudsen <arve.knudsen@gmail.com>

* Update contribute/style-guides/e2e.md

Co-Authored-By: Arve Knudsen <arve.knudsen@gmail.com>

* Update contribute/style-guides/e2e.md

Co-Authored-By: Arve Knudsen <arve.knudsen@gmail.com>

* Update contribute/style-guides/e2e.md

Co-Authored-By: Arve Knudsen <arve.knudsen@gmail.com>

* Update contribute/style-guides/e2e.md

Co-Authored-By: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Update contribute/style-guides/e2e.md

Co-Authored-By: Arve Knudsen <arve.knudsen@gmail.com>

* Update contribute/style-guides/e2e.md

Co-Authored-By: Diana Payton <52059945+oddlittlebird@users.noreply.github.com>

* Docs: Breaks a long sentance in two

contribute/developer-guide.md

@@ -94,7 +94,9 @@ go test -v ./pkg/...
 
 ### Run end-to-end tests
 
-The end-to-end tests in Grafana uses [puppeteer](https://github.com/GoogleChrome/puppeteer) to run automated scripts in a headless Chrome browser. To run the tests:
+The end to end tests in Grafana use [Cypress](https://www.cypress.io/) to run automated scripts in a headless Chromium browser. Read more about our [e2e framework](/contribute/style-guides/e2e.md). 
+
+To run the tests:
 
 ```
 yarn e2e-tests

contribute/style-guides/e2e.md

+# End to end test framework
+Grafana Labs uses a minimal home grown solution built on top of Cypress for our end to end (e2e) tests. 
+
+## Basic concepts
+Here is a good introduction to e2e best practices: https://martinfowler.com/bliki/PageObject.html.
+- `Selector`: A unique identifier that is used from the e2e framework to retrieve an element from the Browser 
+- `Page`: An abstraction for an object that contains one or more `Selectors`
+- `Flow`: An abstraction that contains a sequence of actions on one or more `Pages` that can be reused and shared between tests
+
+## Basic example
+Let's start with a simple example with a single selector. For simplicity, all examples are in JSX.
+
+In our example app, we have an input that we want to type some text into during our e2e test.
+```jsx harmony
+<div>
+    <input type="text" className="gf-form-input login-form-input"/>
+</div>
+```
+
+We could define a selector using `JQuery` [type selectors](https://api.jquery.com/category/selectors/) with a string like `'.gf-form-input.login-form-input'` but that would be brittle as style changes occur frequently. Furthermore there is nothing that signals to future developers that this input is part of an e2e test.
+
+At Grafana, we use `aria-label` as our preferred way of defining selectors instead of `data-*` attributes. This also aids in accessibility.
+Let's add a descriptive `aria-label` to our simple example.
+```jsx harmony
+<div>
+    <input type="text" className="gf-form-input login-form-input" aria-label="Username input field"/>
+</div>
+```
+
+Now that we added the `aria-label` we suddenly get more information about this particular field. It's an input field that represents a username, but there it's still not really signaling that it's part of an e2e test.
+
+The next step is to create a `Page` representation in our e2e test framework to glue the test with the real implementation using the `pageFactory` function. For that function we can supply a `url` and `selectors` like in the example below:
+```typescript
+export const Login = pageFactory({
+  url: '/login', // used when called from Login.visit()
+  selectors: {
+    username: 'Username input field', // used when called from Login.username().type('Hello World')
+  },
+});
+```
+
+The next step is to add the `Login` page to the exported const `Pages` in `packages/grafana-e2e/src/pages/index.ts` so that it appears when we type `e2e.pages` in our IDE.
+```ecmascript 6
+export const Pages = {
+  Login,
+  ...,
+  ...,
+  ...,
+};
+
+```
+Now that we have a `Page` called `Login` in our `Pages` const we can use that to add a selector in our html like shown below and now this really signals to future developers that it is part of an e2e test.   
+```jsx harmony
+<div>
+    <input type="text" className="gf-form-input login-form-input" aria-label={e2e.pages.Login.selectors.username}/>
+</div>
+```
+
+The last step in our example is to use our `Login` page as part of a test. The `pageFactory` function we used before gives us two things: 
+- The `url` property is used whenever we call the `visit` function and is equivalent to the Cypress function [cy.visit()](https://docs.cypress.io/api/commands/visit.html#Syntax).
+- Any defined selector in the `selectors` property can be accessed from the `Login` page by invoking it and this is equivalent to the result of the Cypress function [cy.get(...)](https://docs.cypress.io/api/commands/get.html#Syntax).
+```ecmascript 6
+describe('Login test', () => {
+  it('Should pass', () => {
+    e2e.pages.Login.visit();
+    e2e.pages.Login.username().type('admin');
+  });
+});
+```
+
+## Advanced example
+Let's take a look at an example that uses the same `selector` for multiple items in a list for instance. In this example app we have a list of data sources that we want to click on during an e2e test.
+
+```jsx harmony
+<ul>
+  {dataSources.map(dataSource => (
+    <li className="card-item-wrapper" key={dataSource.id}>
+      <a className="card-item" href={`datasources/edit/${dataSource.id}`}>
+        <div className="card-item-name">
+          {dataSource.name}
+        </div>
+      </a>
+    </li>
+  ))}
+</ul>
+```
+```
+
+Just as before in the basic example we'll start by creating a page abstraction using the `pageFactory` function: 
+```typescript
+export const DataSources = pageFactory({
+  url: '/datasources',
+  selectors: {
+    dataSources: (dataSourceName: string) => `Data source list item ${dataSourceName}`,
+  },
+});
+```
+You might have noticed that instead of a simple `string` as the `selector`, we're using a `function` that takes a string parameter as an argument and returns a formatted string using the argument.
+
+Just as before we need to add the `DataSources` page to the exported const `Pages` in `packages/grafana-e2e/src/pages/index.ts`.
+
+The next step is to use the `dataSources` selector function as in our example below:
+```jsx harmony
+<ul>
+  {dataSources.map(dataSource => (
+    <li className="card-item-wrapper" key={dataSource.id}>
+      <a className="card-item" href={`datasources/edit/${dataSource.id}`}>
+        <div className="card-item-name" aria-label={e2e.pages.DataSources.selectors.dataSources(dataSource.name)}>
+          {dataSource.name}
+        </div>
+      </a>
+    </li>
+  ))}
+</ul>
+```
+
+When this list is rendered with the data sources with names `A`, `B`, `C` the resulting html would become:
+```jsx harmony
+<div class="card-item-name" aria-label="Data source list item A">
+ A
+</div>
+...
+<div class="card-item-name" aria-label="Data source list item B">
+ B
+</div>
+...
+<div class="card-item-name" aria-label="Data source list item C">
+ C
+</div>
+```
+
+Now we can go ahead and write our test and the one thing that differs from the `Basic example` is that we pass in which data source we want to click on as an argument to the selector function:
+```ecmascript 6
+describe('List test', () => {
+  it('Clicking on data source named B', () => {
+    e2e.pages.DataSources.visit();
+    e2e.pages.DataSources.dataSources('B').click();
+  });
+});
+```