granted: add tests for assume binary

Verify that assume, assumego, and assume.fish are installed
to prevent regression.

Author: emmanuel.john

Formula/g/granted.rb

@@ -30,5 +30,9 @@ def install
 
     output = shell_output("#{bin}/granted auth configure 2>&1", 1)
     assert_match "[✘] please provide a url argument", output
+
+    assert_predicate bin/"assume", :exist?
+    assert_predicate bin/"assumego", :exist?
+    assert_predicate bin/"assume.fish", :exist?
   end
 end