Tests: internal/community

internal/community · 17 tests

Each test is named for the property it holds, and runs against a real deployment: there is no mock of the database and no arm that skips when it is absent. The sentence is the test's name read back; the name is what go test -run takes.

community_test.go

• Every group is internally connected — TestEveryGroupIsInternallyConnected
• The partition covers the graph exactly once — TestThePartitionCoversTheGraphExactlyOnce. Every entity is in exactly one group.
• The same graph always partitions the same way — TestTheSameGraphAlwaysPartitionsTheSameWay
• The order edges arrive in does not change the answer — TestTheOrderEdgesArriveInDoesNotChangeTheAnswer. The same edges in a different order are the same graph.
• Group numbers are stable across runs — TestGroupNumbersAreStableAcrossRuns. And the group numbers are stable too, not only the grouping.
• Four unconnected subjects are four subjects — TestFourUnconnectedSubjectsAreFourSubjects. A person's memory is not one giant component with noise around it.
• An unconnected entity is its own subject — TestAnUnconnectedEntityIsItsOwnSubject. An entity mentioned once, connected to nothing, is a subject with one member rather than something to discard.
• One relation between two dense subjects does not merge them — TestOneRelationBetweenTwoDenseSubjectsDoesNotMergeThem. Two dense subjects joined by one relation are two subjects.
• A level exists only where a group was too large — TestALevelExistsOnlyWhereAGroupWasTooLarge. A level exists exactly where a group was too large to be one subject and was split again, so the depth of the tree is a property of the memory rather than a number somebody chose.
• Every child is a subset of its parent — TestEveryChildIsASubsetOfItsParent. A child is a subset of its parent.
• A group nothing divides is left whole — TestAGroupNothingDividesIsLeftWhole. A group nothing divides is left alone even when it is over the bound.
• The hierarchy is reproducible — TestTheHierarchyIsReproducible. The hierarchy is as reproducible as the partition under it, including the identifiers — a stored community id that moved between runs would point at a different subject.
• A graph refuses what it cannot place — TestAGraphRefusesWhatItCannotPlace
• Repeated relations between one pair are one edge — TestRepeatedRelationsBetweenOnePairAreOneEdge. The same pair asserted five times is one connection of weight five, not five connections.
• A relation to itself is not an edge — TestARelationToItselfIsNotAnEdge. A relation from something to itself informs no grouping decision — a node is already in its own group — and counting it would distort the density every move is measured against.
• An empty graph has no subjects — TestAnEmptyGraphHasNoSubjects. A graph with nothing in it partitions into nothing, rather than into one empty group.
• A member connected only outwards survives a split — TestAMemberConnectedOnlyOutwardsSurvivesASplit. A member of a group whose every relation points outside it has no place in the induced subgraph, and dropping it would lose a member of the community it belongs to.