A pre-run modifier

Chapter lab: Shaping data and resultsch21-shaping-data-and-results.zip · 4 KB

This chapter works in a prepared project. Download it before the first task; it unpacks into its own folder.

Download ch21-shaping-data-and-results.zip

Or fetch and unpack it from a terminal in VS Code:

bash / zsh
PowerShell

curl -fsSLO https://manykarim.github.io/robotframework-essentials-web/labs/ch21-shaping-data-and-results.zip && unzip -q ch21-shaping-data-and-results.zip && rm ch21-shaping-data-and-results.zip

Invoke-WebRequest https://manykarim.github.io/robotframework-essentials-web/labs/ch21-shaping-data-and-results.zip -OutFile ch21-shaping-data-and-results.zip; Expand-Archive ch21-shaping-data-and-results.zip -DestinationPath .; Remove-Item ch21-shaping-data-and-results.zip

Open the folder in VS Code with code rfe-ch21-shaping-data-and-results (or File → Open Folder…) and accept the recommended RobotCode and Python extensions. Then set it up:

uv sync

bash / zsh
PowerShell

python3 -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt

python -m venv .venv
.venv\Scripts\Activate.ps1
pip install -r requirements.txt

Keep the environment active in every terminal where you run lesson commands.

poetry install --no-root

Python 3.13 or newer is required; uv installs it when it is missing.

Open in browserNo setup? Try the lab right here: its files, an editor and a terminal, running in your browser.

What's inside

Directoryrfe-ch21-shaping-data-and-results/
- Directory.vscode/
  - extensions.json
- Directorychecks/
  - orders.robot
- Directorydata/
  - orders.csv
- Directoryext/
  - README.md
- .gitignore
- .python-version
- LAB.md
- pyproject.toml
- README.md
- requirements.txt
- uv.lock

A listener observes a run. A pre-run modifier changes it — before any test executes. It is a SuiteVisitor: Robot Framework walks your suites and calls your visit methods, and you edit what is there. Select a subset, skip tests, add tags, reorder — all decided from code, at run time.

You attach one with --prerunmodifier. Overriding start_suite(self, suite) lets you rewrite suite.tests before the suite runs.

Task 1 — Keep only the smoke tests

Edit

Goal: create ext/SmokeOnly.py — a SuiteVisitor whose start_suite keeps only the tests tagged smoke.

Here is the same base class doing a different edit — adding a tag. Adapt it to filter to smoke-tagged tests instead.

Worked example — adapt it, don’t copy it

from robot.api import SuiteVisitor


class TagOrders(SuiteVisitor):
    def start_suite(self, suite):
        for test in suite.tests:
            if "Order" in test.name:
                test.tags.add("orders")

Done when

ext/SmokeOnly.py defines a SuiteVisitor.

Hint 1

Subclass the visitor and override start_suite: class SmokeOnly(SuiteVisitor): with def start_suite(self, suite):.

Hint 2

Replace the suite’s tests with just the smoke-tagged ones: suite.tests = [t for t in suite.tests if "smoke" in t.tags].

Solution

from robot.api import SuiteVisitor


class SmokeOnly(SuiteVisitor):
    def start_suite(self, suite):
        suite.tests = [test for test in suite.tests if "smoke" in test.tags]

Task 2 — Run with your modifier

Run

The bundled checks/orders.robot has two smoke-tagged tests and two that are not. Attach your modifier:

uv run robot --prerunmodifier ext/SmokeOnly.py checks/orders.robot

robot --prerunmodifier ext/SmokeOnly.py checks/orders.robot

poetry run robot --prerunmodifier ext/SmokeOnly.py checks/orders.robot

Only the two smoke tests run — the others were removed before execution.

Done when

with the modifier, only the smoke-tagged tests run.

Check your understanding

Quick recall. Your first answer stays in this browser; the quiz never blocks your progress.

A pre-run modifier changes a run…
Show the answer
Answer: before any test executes — A SuiteVisitor attached with --prerunmodifier edits the test data before execution.
Which base class does a pre-run modifier extend?
Show the answer
Answer: SuiteVisitor — It is a SuiteVisitor; override start_suite to rewrite suite.tests.

Key terms

SuiteVisitorconcept: Walk the running model; a pre-run modifier subclasses it.
--prerunmodifiercommand: Attach a modifier that edits tests before they run.

All terms in the glossary →