src/main/java/com/google/devtools/build/docgen/templates/attributes/test/env.html

<p><code>Dictionary of strings; optional; values are subject to
<a href="${link make-variables#location}">$(location)</a> and
<a href="${link make-variables}">"Make variable"</a> substitution</code>
</p>

<p>Specifies additional environment variables to set when the test is
  executed by <code>bazel test</code>.
</p>

<p>
  This attribute only applies to native rules, like <code>cc_test</code>, <code>py_test</code>,
  and <code>sh_test</code>.  It does not apply to Starlark-defined test rules.
</p>