Azure Build Pipeline: How to pass a "multiline variable" to a build template?

Question

I have this Azure build pipeline, which starts a VSTest Task. It should test all projects that end with "Unittest.csproj", but it should exclude test projects that end with "Common.Unittest.csproj":

# my-azure-pipeline.yaml:

...
steps:
- task: VSTest@2
  inputs:
    testSelector: 'testAssemblies'
    testAssemblyVer2: |
      **/*Unittest.csproj
      ! **/*Common.Unittest.csproj
...

This works fine.

As I have a couple of similar builds, I want to extract a build template (myTemplate.yaml), which now uses a variable $(testprojects) for value "testAssemblyVer2":

# myTemplate.yaml

...
steps:
- task: VSTest@2
  inputs:
    testSelector: 'testAssemblies'
    testAssemblyVer2: $(testProjects)
...

Now I tried to set the variable like this, but no luck:

# my-azure-pipeline.yaml

...
variables:
  - testProjects: |
      **/FistUnittestProject.csproj
      ! **/SecondUnittestProject.csproj
    
extends:
  template: myTemplate.yaml
...

I wonder which is the proper way to define a "multiline thing" via a variable?

Any help appreciated.

Answer 1

As of this time, however, creating multiline variables in Azure DevOps is not supported. You can vote on this user voice. The Microsoft product team will seriously consider the proposal, if it gets enough votes.

As an alternative method, you can use PowerShell task to output a line break to set a multiline variable.

For detailed steps, please refer to this answer. I have tested it and it works perfectly.