I know how to write a function that streams input from the pipeline. I can reasonably tell by reading the source for a function if it will perform properly. However, is there any method for actually testing for the correct behavior?
I accept any definition of "testing"... be that some manual test that I can run or something more automated.
If you need an example, let's say I have a function that splits text into words.
PS> Get-Content ./warandpeace.txt | Split-Text
How would I check that it streams input from the pipeline and begins splitting immediately?
Ah, I've got a very simple solution. The concept is to insert your own step into the pipeline with obvious side-effects before the function that you're testing. For example...
PS> 1..10 | %{ Write-Host $_; $_ } | function-under-test
If your function-under-test is "bad", you will see all of the output from 1..10 twice, like this
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1
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3
If the function-under-test is processing items lazily from the pipeline, you'll see the output interleaved.
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1
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