Integration in pipeline example is not ok for multiple test libraries

### Type of issue

Typo

### Description

We are implementing unit testing using microsoft.testing.plaform. The documentation describes how to integrate this into a pipeline. However, it simply states:

`To run a test project in CI add one step for each test executable that you wish to run, such as this on Azure DevOps`

This is not ideal for several reasons:

Performance:
if you have 100 testing projects from which tests need to run. When we do this, all these test assemblies are being run serially, making the pipeline REALLY slow. When running these tests in visual studio, it takes about 30 seconds. Running them in the pipeline serially takes over 20 minutes. We need a way to properly run tests from different assemblies in the same solution in parallel to speed up the process.

Maintainability:
We regularly add testing projects to our solution. It would be very nice if we didn’t have to change the pipeline every time we add a project, and we could simply state to run all tests in a solution

Performance is the main issue here though. So we would like to see the documents include an example for how to integrate this when you have multiple test projects you want to run in parallel.

### Page URL

https://learn.microsoft.com/en-us/dotnet/core/testing/unit-testing-platform-intro?tabs=continuous-integration

### Content source URL

https://github.com/dotnet/docs/blob/main/docs/core/testing/unit-testing-platform-intro.md

### Document Version Independent Id

25fa6833-57fb-40f0-388f-433c99fee207

### Article author

@Evangelink

### Metadata

* ID: 53bb5ce6-d5ae-8b7f-8b16-0864f3715e38
* Service: **dotnet-fundamentals**

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