Your test doesn’t initialize required data or relationships.

Problem Explanation

Tests run with SeeAllData=false by default, so missing records cause null references.

Root Cause(s)

1. Missing lookup record creation

2. Query returns empty list

3. Static variables not reset

Step-by-Step Solution

1. Create all required test data explicitly

2. Use defensive null checks

3. Assert query results before access

Edge Cases & Variations

1. Triggers may expect org-level settings

2. Platform events behave differently in tests

Common Mistakes to Avoid

1. Assuming org data exists

2. Skipping assertions