Add tests for every implemented command

tests/service_expose.bats

@@ -0,0 +1,30 @@
+#!/usr/bin/env bats
+load test_helper
+
+setup() {
+  dokku "$PLUGIN_COMMAND_PREFIX:create" l >&2
+}
+
+teardown() {
+  dokku --force "$PLUGIN_COMMAND_PREFIX:destroy" l >&2
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:expose) error when there are no arguments" {
+  run dokku "$PLUGIN_COMMAND_PREFIX:expose"
+  assert_contains "${lines[*]}" "Please specify a name for the service"
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:expose) error when service does not exist" {
+  run dokku "$PLUGIN_COMMAND_PREFIX:expose" not_existing_service
+  assert_contains "${lines[*]}" "service not_existing_service does not exist"
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:expose) success when not providing a custom port" {
+  run dokku "$PLUGIN_COMMAND_PREFIX:expose" l
+  [[ "${lines[*]}" =~ exposed\ on\ port\(s\)\ [[:digit:]]+ ]]
+}
+
+@test "($PLUGIN_COMMAND_PREFIX:expose) success when providing a custom port" {
+  run dokku "$PLUGIN_COMMAND_PREFIX:expose" l 4242
+  assert_contains "${lines[*]}" "exposed on port(s) 4242"
+}