A test plan is a project-specific document detailing scope, approach, resources, schedule, and deliverables for testing a particular product/release. A test strategy is a higher-level, often organization-wide document defining the general testing approach and standards.
The test plan (owned by the test lead/manager) covers: objectives, scope (in/out), test items, features to test, approach, entry/exit criteria, environment, schedule, roles, risks, and deliverables. The test strategy is broader and more static — testing types, tools, automation approach, defect-management process, standards — applied across projects. In practice, a project's test plan references or aligns with the org's test strategy. Some organizations merge them. Knowing the distinction (plan = project-specific/dynamic, strategy = organizational/static) is a common interview question.
The company's test strategy mandates automation of regression and a defined defect-severity scale; each release's test plan then specifies that release's scope, environment, schedule, and exit criteria within those standards.
How does a test plan differ from a test strategy?