Decouple tests from implementation

// GOOD
import { DEFAULT_GIT_DIFF_LINE_LIMIT } from "./viewDiff";

test("viewDiff should truncate diffs exceeding line limit", async () => {
  const largeInput = Array(DEFAULT_GIT_DIFF_LINE_LIMIT + 1).fill("test line");
  // ...
});

// BAD
test("viewDiff should truncate diffs exceeding line limit", async () => {
  const DEFAULT_GIT_DIFF_LINE_LIMIT = 5000; // Duplicated constant
  // Test will break if implementation changes the limit
  // ...
});

// GOOD
test("should use the default TTL value", () => {
  const anthropic = new Anthropic({/* config */});
  const defaultTtl = anthropic.getDefaultTtl(); // Get actual implementation value
  
  const result = anthropic.convertMessages(messages);
  expect(result[0].content[0].cache_control.ttl).toBe(defaultTtl);
});

// BAD
test("should use default TTL when not specified", () => {
  // Assumes '5m' is the default without verification
  expect(result.content[0].cache_control.ttl).toBe("5m");
});

// GOOD - Tests behavior without assuming structure
test("should contain expected rule names", () => {
  const applicableRules = getApplicableRules();
  expect(getRuleNames(applicableRules)).toContain("Global Rule");
});

// BAD - Tightly coupled to structure
test("should contain expected rule names", () => {
  const applicableRules = getApplicableRules();
  expect(applicableRules.map(r => r.rule.name)).toContain("Global Rule");
});