Wrap file IO functions

[tangrufus]

• I've read the guidelines for Contributing to Roots Projects
• This request isn't a duplicate of an existing request
• This is not a personal support request that should be posted on the Roots Discourse community

Summary

Wrap file IO functions, something like:

trellis-cli/cmd/main.go

Line 7 in 9900ff9

var execCommand = exec.Command

trellis-cli/cmd/cmd_test.go

Lines 19 to 25 in 9900ff9

	func mockExecCommand(command string, args ...string) *exec.Cmd {
	cs := []string{"-test.run=TestHelperProcess", "--", command}
	cs = append(cs, args...)
	cmd := exec.Command(os.Args[0], cs...)
	cmd.Env = []string{"GO_WANT_HELPER_PROCESS=1"}
	return cmd
	}

Motivation

Currently, tests that perform file IO might fail because files might not exist. Leaving them only testable in integration test.

Wrapping file IO functions makes uniting tests (go test -short) possible (like mockExecCommand).

[swalkinshaw]

Makes sense 👍 I'd have to look around since I don't know much about Go testing