Testing Strategy — Simple

flowchart TB
  E2E[E2E - browser, real stack<br/>few]
  INT[Integration<br/>some]
  UNIT[Unit<br/>many]
  UNIT --> INT --> E2E

  classDef u fill:#d1fae5,stroke:#065f46,stroke-width:1px,color:#0f172a;
  classDef i fill:#fef3c7,stroke:#92400e,stroke-width:1px,color:#0f172a;
  classDef e fill:#fee2e2,stroke:#991b1b,stroke-width:1px,color:#0f172a;
  class UNIT u;
  class INT i;
  class E2E e;

    classDef client fill:#dbeafe,stroke:#1e40af,stroke-width:1px,color:#0f172a;
    classDef edge fill:#cffafe,stroke:#0e7490,stroke-width:1px,color:#0f172a;
    classDef service fill:#fef3c7,stroke:#92400e,stroke-width:1px,color:#0f172a;
    classDef datastore fill:#fee2e2,stroke:#991b1b,stroke-width:1px,color:#0f172a;
    classDef cache fill:#fed7aa,stroke:#9a3412,stroke-width:1px,color:#0f172a;
    classDef queue fill:#ede9fe,stroke:#5b21b6,stroke-width:1px,color:#0f172a;
    classDef compute fill:#d1fae5,stroke:#065f46,stroke-width:1px,color:#0f172a;
    classDef storage fill:#e5e7eb,stroke:#374151,stroke-width:1px,color:#0f172a;
    classDef external fill:#fce7f3,stroke:#9d174d,stroke-width:1px,color:#0f172a;
    classDef obs fill:#f3e8ff,stroke:#6b21a8,stroke-width:1px,color:#0f172a;
    class E2E client;
    class INT,UNIT service;

The test pyramid: many fast unit tests at the base, fewer integration tests in the middle, a handful of end-to-end at the top. The opposite shape (the "ice-cream cone") is what slow, flaky test suites look like.