Let us create a simple test method related to trigger to act as workflow with field update blog written earlier. Without further ado:
You can right click the image above and select 'Open image in new tab' if you are using Google Chrome to get better image resolution or get the text version from this URL.
Let me give a quick explanation on the code above:
- We start with creation of record in reference object Iso_Country_Mapping__c and populate Country Code and Country Name
- Continue with Account creation, then update Billing Country of Account
- The first 2 test methods are Positive test case
- The last one for Negative test case, USA is not valid country, only US or United States
Once the code save successfully (Salesforce will check the code for any syntax error, it will not allow you to save if any error), you can click button 'Run Test' to execute the test method and see the result.
Now, go back to your the trigger and look for Code Coverage, if nothing wrong it should be updated, remember we need at least 75%, if you can achieve 100% is perfect. Code above cover for 91% as screenshot below
The test method show here is very simple using single record of positive and negative test case, but in many scenarios, you can enhance with multiple records test case and testing as other users.
Reference: Testing Example