Contract Impact Test Design — 4.0

Purpose

Turn verified impact surfaces into an executable QA-oriented test design.

This skill exists because:

FUNCTION IMPACT != API CONTRACT IMPACT != TEST DESIGN

A list of impacted methods is not a test plan. A list of impacted endpoints is not a test matrix.

The skill must connect:

change / requirement
→ external operation
→ request contract
→ runtime selection
→ integration / state behavior
→ observable result
→ test viewpoint
→ Check ID

Inputs

Use the strongest available evidence in this order:

1. explicit requirement/specification
2. current source
3. promoted verified reverse-engineering baseline
4. source-backed patch impact report
5. patch/diff as candidate future behavior
6. existing tests as behavioral evidence, not unquestioned truth

Do not invent missing contracts or expected results.

Step 0 — Canonical Requirement / Scope Matrix

When an explicit requirement/specification exists, normalize it before deriving tests.

Create:

Rules:

• Evaluate each row independently.
• Do not transfer conditions from one endpoint/operation/surface to another.
• A condition applies only where the requirement explicitly assigns it.
• Preserve explicit exclusions and non-applicable surfaces.
• If scope cannot be proven, mark it SCOPE_UNRESOLVED.
• Use this matrix as the authoritative scope for later test derivation.

This prevents a condition from one operation from leaking into another operation's test oracle.

Step 1 — Impacted External Operation Inventory

For every material impact, identify all externally reachable operations that can observe it.

Possible entry types include:

• REST API
• CLI
• scheduled job
• message/event consumer
• file/config import
• other source-confirmed public interfaces

For REST, record:

If no external operation is reachable, classify and prove:

NO_DIRECT_EXTERNAL_INTERFACE_IMPACT

Do not stop at class/method names.

Step 2 — Request Contract Inventory

For every impacted REST operation enumerate the request dimensions needed to reach and distinguish affected behavior.

GET / DELETE

Inspect:

• path params
• query params
• headers
• required/optional
• omitted behavior
• empty/null where representable
• defaults
• enum/range/format
• selector rules
• parameter combinations

POST / PUT / PATCH

Inspect all of the above plus:

• content type
• body DTO/model
• body required/optional
• top-level fields
• relevant nested fields
• arrays/collections where relevant
• null/empty/default
• enum/range/format
• cross-field combinations

Create:

Do not restrict inventory to newly added fields. Include existing selectors/fields needed to reach the impacted runtime path.

Step 2A — Input / Parameter Semantics Gate

When the interface accepts named parameters or structured inputs, keep these classes distinct:

• valid supported parameter/input
• unsupported parameter/input name
• wrong-case parameter/input name
• invalid value of a supported parameter/input
• invalid combination of supported parameters/inputs
• omitted / null / empty / default, when applicable

Do not conflate them.

If the specification defines case sensitivity, unsupported-input behavior, defaults, or ignore rules, preserve those semantics exactly.

Do not infer an error oracle merely because an input is unknown or malformed. The expected result must come from requirement/specification or verified source behavior.

Step 3 — Preconditions and Environment Dimensions

Identify source/requirement-backed conditions such as:

• storage/product/model
• upgraded/non-upgraded state
• feature flags
• authentication/authorization role
• existing resource state
• real/virtual classification
• integration availability
• persisted/configured state

Create equivalence classes rather than arbitrary examples.

Step 4 — Observable Behavior Inventory

For every impacted path identify applicable expected observables:

API

• HTTP status
• domain/product error code
• response field/value
• field presence/absence
• null/default behavior
• headers if relevant

Integration / command

• command type
• command parameters
• downstream identifier/serial
• call/no-call
• call ordering when relevant
• response parser/normalization behavior

Data / state

• persisted value
• config output
• cache/map identity
• classification outcome
• created/updated/deleted state

If the expected oracle cannot be proven, use:

EXPECTED_BEHAVIOR_UNRESOLVED

and identify exactly what is missing.

Step 4A — Field / Data Provenance Inventory

For every response/output/state value affected by the change, prove the value lifecycle before using it as a test oracle.

Create:

Determine independently:

1. under what condition the source/downstream data is obtained
2. which command/query/call/branch makes it available
3. where it is parsed or decoded
4. where it is transformed or normalized
5. where it is mapped/stored
6. what happens when it is absent or not retrieved
7. how it is serialized/emitted/consumed
8. what externally observable result follows

Important:

• Conditional output behavior may be implemented indirectly by conditional retrieval.
• Do not require an explicit serializer/output-layer condition when upstream retrieval and mapping already guarantee the required observable behavior.
• Current implementation shape is not itself the expected test oracle.
• If provenance cannot be proven, use EXPECTED_BEHAVIOR_UNRESOLVED.

Step 5 — Derive Test Viewpoints

Derive viewpoints from contract and impact dimensions, not methods.

Applicable viewpoints may include:

1. existing-request backward compatibility
2. new behavior positive path
3. feature/condition absent path
4. required parameter/body field omitted
5. optional parameter/body field omitted
6. null/empty/default
7. enum/range/format boundary
8. valid selector combinations
9. invalid selector combinations
10. cross-field combinations
11. upgraded/non-upgraded or version/model variants
12. legacy/unaffected regression
13. correct downstream command/argument
14. downstream call must not occur on validation failure
15. downstream response normalization
16. response field/value/presence
17. HTTP status/domain error mapping
18. persisted/configured/state effect
19. real/virtual or equivalent classification outcome
20. integration error handling when source defines it

Do not create a viewpoint when source proves it irrelevant.

Step 5A — Test Oracle Chain

For every Check ID involving changed output/data, the expected result must be traceable as:

requirement / verified expected rule
→ trigger / request condition
→ expected source/downstream data availability
→ expected transform/mapping/state
→ expected serialization/output
→ externally observable result

Do not derive expected behavior solely from current implementation. Do not create a serializer-level expectation when the observable condition is enforced earlier in the data flow.

If any material link is unproven, mark the case:

BLOCKED_MISSING_ORACLE

and name the missing evidence.

Step 6 — Combination Strategy

Do not blindly generate the Cartesian product.

Use, in order:

1. explicit requirement combinations
2. source validation branches
3. equivalence partitioning
4. boundary-value analysis
5. decision-table combinations
6. pairwise/risk-based combinations for independent dimensions
7. regression cases for unchanged behavior

HIGH/CRITICAL impacts require direct coverage of each material branch.

Step 7 — Assign Check IDs

Assign stable IDs:

001
002
003
...

Each Check ID must represent one coherent scenario with:

• precondition
• operation
• concrete request setup
• expected runtime/integration behavior
• expected API/domain result
• expected response/state

Do not combine materially different request variants under one Check ID.

Step 8 — Spreadsheet-Style Cross Matrix

Generate a cross matrix where columns are Check IDs and rows are conditions/confirmation items.

Required row groups when applicable:

Precondition
API
  Method + endpoint
  Path parameters
  Query parameters
  Headers
  Body / payload
Command / downstream interaction
Expected results
  HTTP status
  Domain error
  Response fields/state

Use O to mark a condition applicable to a Check ID.

Example shape:

Check conditions / confirmation items | 001 | 002 | 003
Precondition
  upgraded storage                    |  O  |  O  |
  non-upgraded storage                |     |     | O
API
  GET /4.0/items                       |  O  |  O  |
    query: detail=true                |  O  |     |
    query: detail absent              |     |  O  |
  POST /4.0/items                      |     |     | O
    body.mode=valid                   |     |     | O
Expected results
  HTTP 200                            |  O  |  O  | O

This matrix is mandatory when two or more scenarios exist.

Step 9 — Detailed Test Case Table

Mandatory table:

Levels:

UNIT
COMPONENT
API_CONTRACT
INTEGRATION
END_TO_END
REGRESSION

Rules:

• API-visible impact cannot be covered only by UNIT tests.
• GET rows must include concrete query/path/header setup when relevant.
• POST/PUT/PATCH rows must include concrete payload setup when relevant.
• Validation cases must specify expected downstream call/no-call where provable.
• Expected values must be evidence-backed.

Step 10 — CSV Export

When requested by the calling prompt, create a spreadsheet-friendly CSV with one row per Check ID.

Minimum columns:

CheckID
Level
Precondition
HttpMethod
Endpoint
PathParams
QueryParams
Headers
BodyPayload
ExpectedRuntimeBehavior
ExpectedDataProvenanceOrState
ExpectedHttpStatus
ExpectedDomainError
ExpectedResponseOrState
RegressionPurpose
Evidence

Quote values correctly when they contain commas/newlines.

Traceability Gate

Every material requirement/impact must map to at least one Check ID or an explicit justified no-test classification.

Create:

Coverage statuses:

COVERED
PARTIALLY_COVERED
NOT_COVERED
NOT_APPLICABLE
BLOCKED_MISSING_ORACLE

Completion Gate

The skill MUST NOT complete until all applicable items pass:

[ ] canonical requirement/scope matrix created when an explicit requirement exists
[ ] external operations identified or non-exposure proven
[ ] exact REST method/path captured
[ ] GET path/query/header parameters enumerated
[ ] POST/PUT/PATCH body fields enumerated
[ ] validation, case-sensitivity, unsupported-input, and combination semantics considered
[ ] precondition/environment dimensions considered
[ ] field/data provenance proven for changed output/state or unresolved explicitly
[ ] expected downstream behavior defined or unresolved explicitly
[ ] HTTP/domain/response/state oracle is tied to a requirement + provenance chain or unresolved explicitly
[ ] no condition was transferred from another endpoint/operation without evidence
[ ] Check IDs assigned to concrete scenarios
[ ] cross matrix generated
[ ] detailed testcase table generated
[ ] API-visible impacts have API_CONTRACT-or-higher coverage where feasible
[ ] traceability from impact/requirement to Check IDs exists

If a completion item cannot pass because evidence is missing, report the blocker rather than guessing.

Anti-Patterns

Do NOT produce only:

- changed classes/functions
- impacted methods
- endpoint names without request dimensions
- generic "positive/negative" test bullets
- unit-test method suggestions without API contract cases
- expected behavior inferred from intuition

The target artifact is a contract-level test design, not a code coverage list.