### Question:
SLAAgreementHelper { public String getPowerUsagePerAppUnits() { return getUnits(powerUsagePerApp); } SLAAgreementHelper(String slaString); SLA getSla(); double getPowerUsagePerApp(); String getPowerUsagePerAppUnits(); double getPowerUsagePerOVFId(String ovfId); String getPowerUnitsPerOVFId(String ovfId);  }### Answer:
@Test public void getPowerUsagePerAppUnits() { SLAAgreementHelper helper = new SLAAgreementHelper(slaAgreement2Text); String units = helper.getPowerUsagePerAppUnits(); assertEquals("Watt", units); helper = new SLAAgreementHelper(slaAgreementText); units = helper.getPowerUsagePerAppUnits(); assertNull(units); }