test: adds tests for existing help subcommands

test/nag.bats

@@ -20,6 +20,27 @@ load test_helper
   [[ "${output}" =~ "Options:" ]]
 }
 
+@test "help list shows list usage" {
+  run_nag help list
+  [ "${status}" -eq 0 ]
+  [[ "${output}" =~ "Usage:" ]]
+  [[ "${output}" =~ "nag list" ]]
+}
+
+@test "help at shows at usage" {
+  run_nag help at
+  [ "${status}" -eq 0 ]
+  [[ "${output}" =~ "Usage:" ]]
+  [[ "${output}" =~ "[at] <time> <message...>" ]]
+}
+
+@test "help version shows version usage" {
+  run_nag help version
+  [ "${status}" -eq 0 ]
+  [[ "${output}" =~ "Usage:" ]]
+  [[ "${output}" =~ "( version | --version )" ]]
+}
+
 @test "version shows version" {
   run_nag version
   [ "${status}" -eq 0 ]