Test case interpolation incorrectly replaces "-" with "µµµ"

[sborsje]

String interpolation seems to break in a very specific edge-case.

I've been able to create a minimal test suite to reproduce the problem in Venom 1.0.0, 1.0.1, and the latest from master (1.0.0-rc.7 and older don't have this issue):

---
name: Interpolation POC
vars:
  accept: "text/html"

testcases:
  - name: GetVar
    steps:
      - type: http
        method: GET
        url: "http://example.com"
        assertions:
          - result.statuscode ShouldEqual 200
        vars:
          accept:
            from: result.headers.content-type

  - name: UseVar
    steps:
      - type: http
        method: GET
        url: "http://example.com"
        headers:
          test: "{{ .GetVar.accept }}"
        assertions:
          - result.statuscode ShouldEqual 200
          - result.headers.x-cache ShouldEqual "HIT"
      - type: http
        method: GET
        url: "http://example.com"
        headers:
          test: "{{ .GetVar.accept }}"
        assertions:
          - result.statuscode ShouldEqual 200
          - result.headers.accept-ranges ShouldEqual "bytes"

This yields the following result:

 • Interpolation POC (/tests/interpolation.yml)
 	• GetVar SUCCESS
 	• UseVar FAILURE
Testcase "UseVar", step #1: Assertion "result.headers.acceptµµµranges ShouldEqual \"bytes\"" failed. expected: bytes  got: <nil> (/tests/interpolation.yml:0)

A few things to note:

• In the UseVar testcase, there are 2 steps defined. They both execute the same HTTP request, but look at different headers from the result.
• The first step succeeds, but the second step fails. Note that the assertion tries to look at the acceptµµµranges header, which is incorrect.
• As far as I can tell, this only happens when the test case refers back to a result from a previous test case. If in the example above we replace {{ .GetVar.accept }} with {{ .accept }} (which is defined in the vars key at the top), everything works fine.

In our codebase we use this pattern to execute a login request to generate a JWT token at the beginning of the suite, which we then use as a Authorization header in subsequent testcases.

I've tried to debug this a little bit, and was able to trace back the string interpolation to the following function:
https://github.com/ovh/cds/blob/c80557c58fbb2fc28af3da94385172abefddc9fc/sdk/interpolate/interpolate.go#L49

The Do function yield different output for both test cases when it's called from: https://github.com/ovh/venom/blob/master/process_testcase.go#L209

I'm not really sure where to go from here, because both test cases have similar raw input, yet a very different vars slice. My hunch is that something in the vars slice trips up the interpolation function?

[fsamin]

Thanks for the detailed report.
This is related to a bug in the interpolation lib.
I've just made a PR on this lib to fix it: ovh/cds#6047. I have been able to confirm that the PR fixes your testcase.

I will make a PR on venom once the PR above will be merged on master branch

[sborsje]

Awesome! Thanks, @fsamin! 🎉