Reduce number of docker:// and library:// pulls in e2e tests

[dtrudg]

Type of issue

technical debt

Description of issue

The end to end tests in SingularityCE have historically made heavy use of image pulls from docker:// and library:// sources.

In many cases these are appropriate - we need to actually explicitly test that the functionality operates as expected. However, pulls from the Sylabs library, or Dockerhub, that are just repeating the same operation slow down the e2e process, and increase the risk of failure due to external services rather than issues in the Singularity code.

• Review each usage of a library:// or docker:// URI in the e2e/ go files.
• Identify usage of these sources which is not an explicit test of their functionality, or is a duplication.
• Replace use of the library:// docker:// URI with another means. This could include:
  • Using the standard e2e test image
  • Pulling an image to a temporary SIF once, then using the SIF for the tests
  • Using the local docker registry that is started by the e2e tests, rather than DockerHub