tests: mock systemctl output for listing mount units

overlord/managers_test.go

@@ -198,6 +198,9 @@ func (s *baseMgrsSuite) SetUpTest(c *C) {
 		if out := systemdtest.HandleMockAllUnitsActiveOutput(cmd, nil); out != nil {
 			return out, nil
 		}
+		if out, ok := systemdtest.HandleMockListMountUnitsOutput(cmd, nil); ok {
+			return out, nil
+		}
 		return []byte("ActiveState=inactive\n"), nil
 	})
 	s.AddCleanup(r)

systemd/systemdtest/systemdtest.go

@@ -59,3 +59,34 @@ Type=simple
 	}
 	return output
 }
+
+type MountUnitInfo struct {
+	Description  string
+	Where        string
+	FragmentPath string
+}
+
+// HandleMockListMountUnitsOutput returns the output for systemctl in the case
+// where units have the state as described by states.
+// If `cmd` is the command issued by systemd.Status(), this function returns
+// the output to be produced by the command so that the queried services will
+// appear having the ActiveState and UnitFileState according to the data
+// passed in the `states` map.
+func HandleMockListMountUnitsOutput(cmd []string, mounts []MountUnitInfo) ([]byte, bool) {
+	osutil.MustBeTestBinary("mocking systemctl output can only be done from tests")
+	if cmd[0] != "show" ||
+		cmd[1] != "--property=Description,Where,FragmentPath" {
+		return nil, false
+	}
+	var output []byte
+	for _, mountInfo := range mounts {
+		if len(output) > 0 {
+			output = append(output, byte('\n'))
+		}
+		output = append(output, []byte(fmt.Sprintf(`Description=%s
+Where=%s
+FragmentPath=%s
+`, mountInfo.Description, mountInfo.Where, mountInfo.FragmentPath))...)
+	}
+	return output, true
+}