Rough guidance on record playback.

Writing-End-to-End-Tests-using-AzureTest.md

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+`AzureTest` is a framework written to help Azure SDK developers write tests for Swift that can be recorded and played back without network connectivity. It leverages a customized fork of the `Venmo/DVR` framework, which itself is based on the popular Ruby `VCR` framework.
+
+## Getting Started
+
+1. Within your framework's main target, add `AzureTest.framework` under `General > Frameworks and Libraries`.
+2. In `Package.swift`, add `AzureTest` to the dependencies for your test target.
+
+## Creating Resources
+
+Most tests require some Azure resources to be set up prior to running, and these resources should be cleaned up after the test completes. Mechanisms exists to facilitate this automatically.
+
+1. Within the service folder for your framework (the folder directly beneath `sdk`), add resources to either the `test-resources.bicep` file or `test-resources.json`. This file will be used to deploy resources when your test is run live.
+2. If you need to do further setup with the resources created in step 1, add or modify the `test-resources-pre.ps1` or `test-resources-post.ps1` scripts to perform any necessary setup. By default, you can only use Powershell cmdlets. The necessary outputs from these scripts should be dumped into a file called `test-settings.plist` (see below).
+
+## Storing Credentials
+
+1. Create a class which implements `AzureTest.TestSettingsProtocol`. This model should consist of string-based properties which back credentials you need to supply to run tests live.
+2. Within your `Tests` folder, create a plist file named `test-settings.plist` (MUST be an exact match) and add it to the project. This file is part of the `.gitignore` and thus will not be committed as a change in source control.
+3. Within the `setUp` or `setUpWithError` methods of your test class, load your settings by invoking the static `loadFromPlist()` method from your settings model type. This will deserialize the contents of `test-settings.plist` and make the values available for use in your test.
+
+## Writing Tests
+
+1. Within the `Tests` folder, create a new "Unit Test Case Class" in Xcode and import `AzureTest` along with any other necessary imports.
+2. Load your test settings as described above and use those values to create any client you need.
+3. Load the value of the environment variable `TEST_MODE` by writing: `private var mode = environmentVariable(forKey: "TEST_MODE", default: "playback")`. If the value is anything except "live", pass along a `DVRSessionTransport` object in the `TransportOptions` passed to the client.