This AZ-400 practice question tests your understanding of design and implement build and release pipelines. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Your team uses GitHub for source control and Azure Pipelines for CI/CD. You need to trigger a pipeline automatically when a pull request is created against the main branch. Which trigger type should you configure in the YAML pipeline?
pr:
Correct: pr trigger fires on pull requests.
trigger:
Why wrong: trigger is for push events, not pull requests.
schedules:
Why wrong: schedules is for cron-based triggers.
resources:
Why wrong: resources is for other pipelines, not triggers.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
pr:
Option A is correct because the `pr:` trigger in Azure Pipelines YAML is specifically designed to automatically start a pipeline when a pull request is created or updated against a specified branch. By default, `pr:` triggers are enabled for the `main` branch, so configuring `pr: main` ensures the pipeline runs on PR creation without needing a separate branch policy.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
pr:
Why this is correct
Correct: pr trigger fires on pull requests.
Related concept
Read the scenario before looking for a memorised answer.
trigger:
Why it's wrong here
trigger is for push events, not pull requests.
schedules:
Why it's wrong here
schedules is for cron-based triggers.
resources:
Why it's wrong here
resources is for other pipelines, not triggers.
Common exam traps
The trap here is that candidates often confuse `trigger:` (CI on push) with `pr:` (PR validation), especially since both can be used for the same branch, but they serve different events and have distinct YAML syntax.
Detailed technical explanation
Under the hood, the `pr:` trigger works by listening to GitHub webhook events for `pull_request` actions (opened, synchronize, reopened). Azure Pipelines automatically creates a webhook subscription in the GitHub repository when the YAML pipeline is first run, and the pipeline runs with the merge commit of the PR, not the source branch head, to validate the merge result. A subtle behavior is that if you set `pr: none`, you can disable PR triggers entirely and rely on branch policies in GitHub to enforce pipeline runs.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
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FAQ
Design and implement build and release pipelines — This question tests Design and implement build and release pipelines — Read the scenario before looking for a memorised answer..
The correct answer is: pr: — Option A is correct because the `pr:` trigger in Azure Pipelines YAML is specifically designed to automatically start a pipeline when a pull request is created or updated against a specified branch. By default, `pr:` triggers are enabled for the `main` branch, so configuring `pr: main` ensures the pipeline runs on PR creation without needing a separate branch policy.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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