Open code, practice, and notes →
Download source with English comments · for reading
Playwright · 12 Invalid Files and Preservation
Series contents · Technology map
Stage: Persistent Data and File Round Trips · External example · preview instructions · Storage ID: playwright-step-12
Goals and learning outcomes
- Learning outcome: explain the role of Validation failure. Input cases: existing notes and two error files.
- Deliverable: error guidance, existing values, and values after reloading. Explain the rationale for handling Negative path, linking it to the code.
Prerequisites
Prepare the experiment results for File input and Restoration result from Unit 11, “File Upload”.
Key concepts and explanations
Validation failure
Invalid JSON must not erase existing data. Examine syntax errors and schema errors separately.
Negative path
Error guidance is also part of the user contract. Check that normal work remains possible after a failure.
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-12.spec.ts in a separate practice project, create existing notes, then upload malformed JSON and a file with an invalid schema. Refer to the existing Unit 1·14·28 examples only as starting points.
- Input conditions: existing notes and two error files. Baseline: JSON syntax. Run under the baseline conditions, then record observations and errors in notes/day-12.md.
- Variable: error; changed value: schema mismatch. Run again through the same input path. Deliverable to save: error guidance, existing values, and values after reloading. Hypothesis to check: Preserve existing data for both errors. Compare it with the actual results, and record whether they agree and why they differ.
Variables to observe
| Variable | Baseline | Change | Expected change / hypothesis |
|---|---|---|---|
| error | JSON syntax | schema mismatch | Preserve existing data for both errors. |
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: error guidance, existing values, and values after reloading. 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: Validation failure and Negative path. For unexpected items, at least 1 cause or reason they remain unresolved is recorded.
Self-check
- Which processing stage does Validation failure affect in this exercise? Input cases: existing notes and two error files.
- Variable: error. Hypothesis to check: Preserve existing data for both errors. Did the actual results agree with the hypothesis? Explain the evidence in terms of Negative path.
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.