While working in a sandbox, an Apex test fails when run in the Test Runner. However, executing the Apex logic in the Execute Anonymous window succeeds with no exceptions or errors. Why did the…

If there were a syntax error, the code would fail to compile or execute in both the Test Runner and Execute Anonymous.

While System.runAs is important for testing different user profiles and sharing rules, its absence alone doesn't explain why a test fails due to data dependencies when Execute Anonymous succeeds.

Calling a future method within a test method itself is generally handled differently (Test.stopTest() causes them to execute synchronously), but this doesn't explain a discrepancy based on data access.

Apex tests, by default, do not have access to existing organizational data; they must create their own test data (using Test.startTest() and Test.stopTest() with DML operations) to ensure repeatable and isolated tests. When the logic runs in Execute Anonymous, it operates in the context of the logged-in user, which does have access to all existing sandbox data, allowing the method to succeed if it implicitly depends on that data.