Testing TDD

Activate

write tests|"TDD"|"test-first"|"red-green-refactor"|add coverage|verify behavior

Cycle

1.RED:write failing test→verify fails for right reason(not syntax) 2.GREEN:minimal impl→just enough to pass→no extras 3.REFACTOR:clean up→DRY→extract→tests still pass

Test Types

|Type|Scope|Speed|Deps|Use For| |Unit|func/method|<ms|mocked|isolated logic| |Integration|components|ms-s|real|interactions| |Edge|boundaries|varies|both|nil/empty/max/errors|

Coverage Principles

• •Test behavior, not implementation
• •Public API, not private helpers
• •Include error paths + edge cases
• •Table-driven for multiple scenarios

Table-Driven Pattern

tests := []struct{name,input,want,wantErr}{}
for _, tt := range tests { t.Run(tt.name, func(t *testing.T){...}) }

Edge Cases Checklist

nil/empty input|zero/negative|boundary values|max+1|concurrent access|error conditions

Anti-patterns

|Bad|Why|Fix| |Test impl details|breaks on refactor|test behavior| |One mega-test|hard to debug|one concept per test| |Flaky tests|timing/random|deterministic deps| |Skip red phase|no TDD discipline|always fail first| |Test private funcs|impl coupling|test via public API|

Quality Gate

• • Fails before impl (red)
• • Passes with minimal code (green)
• • Passes after refactor
• • Name describes behavior
• • Isolated + deterministic
• • Edges + errors covered