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Playwright · 10 Download Events
Series contents · Technology map
Stage: Persistent Data and File Round Trips · External example · preview instructions · Storage ID: playwright-step-10
Goals and learning outcomes
- Learning outcome: explain the role of Event order. Input cases: a backup containing two notes.
- Deliverable: filename, JSON structure, and note values. Explain the rationale for handling File validation, linking it to the code.
Prerequisites
Prepare the experiment results for Persistent state and Completion signal from Unit 9, “Saving and Reloading”.
Key concepts and explanations
Event order
Register the download wait before clicking. Waiting after the click may miss a fast event.
File validation
A download occurring does not mean that its contents are correct. Check the JSON structure and note values too.
Practice setup
First check the execution scope guidance on the example screen. The following describes the environment needed to extend the assignment in a separate project. Write and run all tests in a separate Node project using @playwright/test and a dedicated local test origin. The existing playwright-01·02·03 previews only display test source; they do not run Playwright in the iframe. Write new test files yourself for the assignments and judge whether they pass only from actual runner output. Do not use a user profile or storage used for everyday work; preserve CSP and isolation.
The linked example is a starting point. It does not implement every task below. Complete work beyond its supported scope in a separate project.
Practice tasks
- In tests/day-10.spec.ts in a separate practice project, create waitForEvent('download') first, click export, then call saveAs. Refer to the existing Unit 1·14·28 examples only as starting points.
- Input conditions: a backup containing two notes. Baseline: ASCII. Run under the baseline conditions, then record observations and errors in notes/day-10.md.
- Variable: notes; changed value: Korean text and emoji. Run again through the same input path. Deliverable to save: filename, JSON structure, and note values. Hypothesis to check: Preserve file contents without encoding loss. Compare it with the actual results, and record whether they agree and why they differ.
Variables to observe
| Variable | Baseline | Change | Expected change / hypothesis |
|---|---|---|---|
| notes | ASCII | Korean text and emoji | Preserve file contents without encoding loss. |
Predictions in this table are not measured results. Change one condition at a time and record why the actual result differs.
Completion criteria
- Required deliverable: filename, JSON structure, and note values. Results are available for both the baseline and changed conditions, allowing comparison of 2 conditions; input values and the execution environment are recorded together.
- The explanation of differences between the two conditions connects both concepts: Event order and File validation. For unexpected items, at least 1 cause or reason they remain unresolved is recorded.
Self-check
- Which processing stage does Event order affect in this exercise? Input cases: a backup containing two notes.
- Variable: notes. Hypothesis to check: Preserve file contents without encoding loss. Did the actual results agree with the hypothesis? Explain the evidence in terms of File validation.
Official references
- Playwright Installation and Execution
- Playwright Locators
- Playwright Assertions
- Playwright Downloads
- Playwright Visual comparisons
Linked example and execution scope
Example source · Runtime environments and limits
Runnable standalone Playwright spec and HTTP fixture; preview does not run tests.
Source code and records are not overwritten automatically. Resetting an existing example also preserves your notes.