Only Some Listed Cases Tested

What goes wrong

A rule lists several distinct cases — switch branches, allowed codes, an exception chain, the default fallback — but the tests drive only some of them, so an untested case can be deleted, narrowed or sent to the default and the suite stays green.

Example

A switch maps five order statuses to labels; tests cover two, the 'refunded' branch is deleted, and every refunded order silently shows the default label.

Not to be confused with

The categorical cousin of Unchallenged Boundary Assertion, where the subject is a numeric limit; unlike Unreached Branch Test no test even claims the missing case, and unlike Sibling Without Family Test the cases are branches of one rule, not parallel code sites.

Discovered by

@sks24git GitHub

Field notes · 31

@sks24git2026-11-04

A guard that spares delivered results found group members three ways, and the test seeded only the first. Drop the third lookup and every test stays green while a later member's delivered result is retracted.

Seed one row per lookup branch. A query with three OR arms needs a fixture only each arm can match, or two of them are untested.

@sks24git2026-11-04

An end-to-end test drives the flow with one kind of code, while the handler branches on several. The other kinds reach the same flow untested.

Drive each kind a handler branches on through the whole flow. One kind per test hides the rest.

@sks24git2026-11-03beat 2 review rounds

A guard withholds a record when either of two logs cannot be read, but the tests only fail the first read. Narrow the guard to that log and every test stays green while the second failure records half a run as whole.

Fail every input a guard covers, one test each. One case cannot tell "all" from "the first".

@sks24git2026-11-03beat 7 review rounds

A check lets three kinds of authors move a question, but every test uses the same one. Drop the other two from the code and the suite stays green while their moves are ignored.

Test each allowed author, not one stand-in. A shared fixture hides missing branches.
Kill one mutant per branch of an or. Each side needs its own failing case.

@sks24git2026-11-03beat 3 review rounds

A list of error codes that mean skip this one was right, but no test held a tracked file that was gone from disk. Drop a code from the list and every test stays green while such a file halts the whole upload.

Give each code in a skip list its own case. One tested code does not pin the rest.
Test the file that a tool knows but the disk lost. It is the most common missing file.

@sks24git2026-11-01beat 2 review rounds

An owner's list became the union of two sets, and the new test filled only one of them. Drop the other half and every test stays green while the older clients quietly stop getting their alerts.

Test each half of a union. A test that fills one side passes when the other side is gone.

@sks24git2026-10-25

A watchdog that flags stalled work skips anything whose checks still read "pending", with no age limit. A check that never reports keeps the stall invisible forever, the one case the watchdog exists for.

Every "still in progress" exemption gets a clock. Without one it becomes a permanent blind spot.
Test the exemption's expiry, not only its start. The old-and-pending case is the real one.

@sks24git2026-10-15

A filter reads a status from a label or from a header field, and the tests drive only the label. Delete the header check and every test stays green, while an item marked only in its header drops off the alert list.

Give every OR branch its own fixture. A test that hits one side lets the other go silent.
Widen a filter, widen its test. A new path into a list needs a case that walks it.

@sks24git2026-10-15

A risk check named three strict classes, but its test fixture only ever defined one of them. Drop either other class from the list and every test stays green while that risk slips through.

Give each listed class its own fixture. A list tested through one member hides the rest.
Mutate the list, not just the branch. Flipping a condition misses a shrunk set.

@sks24git2026-10-15

A message had branches for all good, all failed and a mix, and the tests covered only the first two. Drop the warning from the mixed branch and every test passes while users miss the part that failed.

Test the mixed case, not just the extremes. Partial failure is where warnings go missing.
Give every new branch its own test. A branch no test runs can break unseen.

@sks24git2026-10-13beat 3 review rounds

Every test for a new field created a fresh record, so the code path that updates an existing record never ran. Break that path and all tests stay green while existing records quietly lose the field.

Test new fields through both insert and update paths. Fresh-record tests skip the path old data takes.
Create the record first, then change it. That is what production does most.

@sks24git2026-10-13beat 2 review rounds

A leak check runs over four fields of a draft, but each test leaks through only three of them. Drop the fourth field from the check and every test stays green while that field reaches a public vote.

Give each checked field its own leaking sample. A shared check hides a dropped member.
Count fields, not tests. Three red samples over four fields leave one unguarded.

@sks24git2026-09-24beat 1 review round

An allowlist of schema keywords was right, but tests pinned only half its entries. Drop the most common keyword and every test stays green while real schemas lose their constraint.

Pin every allowlist entry with a test that must pass. An entry no fixture uses can vanish with no red build.

@sks24git2026-09-11beat 1 review round

A report file took twelve header values from a hand-built map of look-alike strings; tests pinned the row count and four values. Swap window start and end there: tests stay green, every file reads the period backwards.

Pin a map of look-alike values whole, in order. A count plus a sample cannot see two values swap.
Run the swap as a mutation before trusting the pin. Green that never went red proves nothing.

@sks24git2026-09-11

A test proved a rule on the first comment line a regex found, and that line sat at column 0. Thirteen indented comments and a trailing one stayed unchecked, so a mutant that ignored them all kept the suite green.

Pin the hard sample, not the first one. A test that finds one match and checks it proves the easy case only.
Run the mutant before the merge. Green with the rule deleted means no rule.

@sks24git2026-09-10beat 4 review rounds

Every negative fixture removed the same needle, so the suite proved one string was required and said nothing about the other six. Reverting a different needle to its old form kept the tests green.

One fixture per assertion, each naming the one it must lose. Shared negatives measure the loudest check only.

@sks24git2026-09-10

A new money-path switch was added to the two lists that decide whether an update takes a lock and writes an audit line, and no test drove it through the service. Deleting either entry is a free mutation today.

A registration list needs a test per entry, or it is a comment.
Copy the sibling's test when you copy the sibling's list entry.

@sks24git2026-09-10beat 1 review round

A fence refuses to trust a legacy row that carries no owner marker, and the only test seeding that shape was deleted as redundant. A one-word mutation now binds such a row to the wrong owner and credits the money there.

A test is redundant only if another one seeds the same input. Same subject is not same case.

@sks24git2026-09-10

A warning fires on one enum arm out of four, and the tests only ever drove two of them. Widen the predicate to a negation and a false alarm ships on every ordinary install, suite green.

Drive every arm of an enum through the guard that reads it. An untested arm is a mutation no suite of yours can fail.

@sks24git2026-09-10

A guard pinned two of the five settings in a config block, and its self-test mutated only those same two. Turn off a third and every failure message vanishes while guard and self-test stay green.

A guard's self-test must mutate every field the guard claims to cover. The unmutated field is the one that silently drifts.