04.01.03 — Relationship Testing: Lookup vs Master-Detail

💡 The Problem: Relationships Define Behavior

In Salesforce, relationships are not just links between objects.
They are behavioral switches that define how data behaves when records are deleted, who can see related records, and what kind of automation is possible.

The chosen relationship type directly affects:

• data integrity
• security and sharing
• automation behavior
• performance and platform limits

From a QA perspective, this makes relationship testing one of the highest-risk areas in the data model.

⚙️ The Two Relationship Types from a QA Perspective

Salesforce provides two primary relationship types:

• Master–Detail
• Lookup

Each one enforces a very different set of rules that must be tested explicitly.

1. Data Integrity and Deletion Behavior

The most visible difference between relationship types appears when the parent record is deleted.

Relationship Type	Integrity Model	Deletion Behavior to Test
Master–Detail	Hard integrity	Deleting the parent must automatically delete all child records
Lookup	Soft integrity	Deleting the parent must leave child records intact and nullify the lookup field

Master–Detail: Cascading Delete

In a Master–Detail relationship:

• child records cannot exist without a parent
• deleting the master record triggers an immediate cascade delete

QA focus:

• delete the master record
• verify that all related detail records are deleted
• confirm they are not recoverable as independent records

Lookup: Orphan Records

In a Lookup relationship:

• child records are independent
• deleting the parent sets the lookup field to null

QA focus:

• delete the parent record
• verify the child record still exists
• verify the lookup field is cleared automatically

Important edge case:
If the Lookup field is marked as Required at schema level, deleting the parent will still nullify the field.
The failure appears on the next save of the child record, not during deletion.

2. Security and Sharing Inheritance

Relationships have a major impact on who can see what.

Master–Detail: Inherited Security

In Master–Detail:

• the child record inherits all security from the master
• object-level sharing on the detail object is ignored

QA focus:

• log in as a user without access to the detail object
• grant access to the master record
• verify the user can still see the detail records

This behavior often surprises teams and causes production access leaks if not tested.

Lookup: Independent Security

In Lookup relationships:

• security is evaluated independently for parent and child
• sharing rules and OWD apply separately

QA focus:

• verify that a user may see a child record without seeing the parent
• validate that sharing rules behave consistently for both objects

3. Automation and Roll-Up Summary Fields

Roll-Up Summary Fields are only available in Master–Detail relationships.

They introduce indirect behavior that must be tested carefully.

QA focus:

1. Create a new child record → verify the roll-up recalculates immediately.
2. Update a qualifying child record → verify recalculation.
3. Delete the last child record → verify roll-up resets correctly.
4. Update non-relevant fields → verify no unnecessary recalculation occurs.

Large numbers of child records increase the risk of:

• governor limit breaches
• performance degradation
• delayed recalculations

🚀 Practical QA Techniques

Testing Relationship Limits

Relationships influence how deeply Salesforce must traverse data.

High-risk scenarios to test:

• deep lookup chains (A → B → C → D)
• automation accessing data across multiple levels
• bulk operations triggering roll-up recalculations

These scenarios often expose hidden SOQL query limit issues.

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Reparenting in Master–Detail

Changing the master record on a detail record triggers:

• roll-up recalculation on both old and new parents
• security re-evaluation
• automation side effects

QA focus:

• test reparenting explicitly
• verify data consistency before and after the change
• confirm no orphaned or duplicated roll-up values appear

Custom Logic That Mimics Relationships

Sometimes teams use:

• Lookup relationships
• Validation Rules or Apex

to simulate Master–Detail behavior

QA focus:

• identify custom enforcement logic
• attempt parent deletion
• verify the correct custom error message is shown
• ensure behavior is consistent across UI and API

✅ Summary: Relationship Type Is a Design Decision

Choosing between Lookup and Master–Detail is not just a modeling decision — it is a testing strategy decision.

• Master–Detail requires rigorous testing of cascading deletes, inherited security, and roll-up recalculations.
• Lookup requires careful testing of orphan records, sharing rules, and independent access paths.

Understanding these implications allows QA to:

• anticipate failure modes
• design focused test cases
• prevent data integrity and security issues before they reach production

In Salesforce, relationships don’t just connect data — they define how the system behaves.