The Powerduck Blog
Product updates, engineering notes, and guides for designing, debugging, testing, mocking, and serving MCP tools from one OpenAPI spec.
Browse the guidesA 94% coverage badge counts a trivial getter the same as the branch where a payment fails mid-flight. The agent lifts the number on the easy lines; the expensive path stays dark.
Read articleThe prompt is not a scratchpad. A token, an internal hostname, or customer PII you paste into the agent lives in a log you do not fully control, long after the fix ships.
Read articleQuick answer Short answer: WireMock offers extensive code-level fault injection and delays; a spec-first studio reaches the same edge cases through the contract and keeps the assertions tied to the
Read articleQuick answer Short answer: WireMock is the JVM standard for code-first HTTP stubbing; Powerduck is a spec-first, language-agnostic mock server. The first is unmatched in code-level control on the JVM;
Read articleQuick answer Short answer: Java stubs are expressive and live in the test code; a spec mock is generated from the contract and serves every language. The first is a
Read articleQuick answer Short answer: Code-first stubbing starts from the test and is immediately expressive; spec-first starts from the contract and is correct by construction. The first is a discipline of
Read articleQuick answer Short answer: WireMock matches more conditions than any spec-derived tool, including JSONPath and XPath; a spec mock matches what the contract declares. The first is the right tool
Read articleQuick answer Short answer: A JVM mock is a single-language target; a spec mock is generated from the contract and serves every client. For a polyglot team, the shared contract
Read articleQuick answer Short answer: A managed mock cloud is a hosted service for stubs; the Hub hosts the mock and the docs together from the spec. The first is a
Read articleQuick answer Short answer: Stubs are a code-level description of the responses; contract tests verify the responses against the schema. The first tells the mock what to return; the second
Read articleQuick answer Short answer: Rich templating is a mock designer's strength for bespoke, dynamic responses; a spec-driven mock uses the examples and response schemas you already author. The
Read articleQuick answer Short answer: Both run in CI, but the mock source differs. A dedicated mock CLI runs a separately maintained file; a studio CLI generates the mock from the
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