To reproduce, run in the GOPATH root:
    mkdir z/
    echo -e 'package z\nfunc x() { println("x") }' > z/z.go
    go test -coverprofile=c.out z

Expected behavior:
  c.out created indicating 0% test coverage (no statements of z.go are covered)

Actual behavior:
  No c.out created.

However, if a test file exists:
    echo "package z" > z/z_test.go
    go test -coverprofile=c.out z
    # c.out created showing no statements covered

Then c.out is created as expected.


The current behavior is problematic in my script that automatically generates coverage
for a directory tree -- there is no indication in the output for packages that have no
tests.


Go: go version go1.2rc3 darwin/amd64
OS: OS X 10.8.5