Testing is a critical part of managing the application lifecycle because it helps improve code quality and reduce the operational risks that come with deploying and updating software.
The term shift-left means moving testing activities as early as possible in the development phase instead of waiting until later stages.
To reduce its current security and stability problems, the organization in the sample scenario should include this shift-left approach in its DevOps strategy.
What tests should be part of shift-left testing?
Software development uses many different types of tests. The most important ones for shift-left testing include the following:
1. Unit Tests
Unit tests focus on the smallest testable parts of application code, such as individual functions or methods.
Purpose:
To check whether each small piece of code can perform its intended job on its own, without depending on the rest of the codebase or any external systems.
Key characteristics:
- Fully automated
- Very fast to run (should finish within about 30 seconds)
- Should provide full code coverage, meaning all unit tests together should test the entire codebase
Why they fit shift-left:
Unit testing is ideal for the shift-left approach. It should be applied to all code as early as possible in the development cycle, preferably right at the start of the programming phase.
2. Smoke Tests
Smoke tests check the core functionality of an application in a test environment.
Purpose:
- To decide whether a new build or deployment is stable enough for deeper testing
- To quickly detect major failures
How they work:
- They test the real application, not just isolated components like unit tests
- They do not test how different applications or components work together
-
User actions can be simulated using:
- Browser automation tools
- User interface automation frameworks
Key characteristics:
- Fully automated
- Quick to run
Why they are called smoke tests:
The term comes from the idea that if you see “smoke,” there is a serious problem (“fire”) that must be fixed immediately.
When to run them:
Smoke testing should be done early in the development cycle, as soon as a version of the software with core functionality is available.
This applies to both:
- The application build phase
- The application deployment phase
3. Integration Tests
Integration tests check how different parts of an application work together.
Purpose:
To validate interactions and data flow between components.
Key characteristics:
- Take much longer to run than unit or smoke tests
- Useful when unit or smoke tests are not enough
How to run them in shift-left:
Because they take a long time, it is not practical to run them on every code change.
Instead, they should be:
- Scheduled to run at regular intervals (for example, nightly or on a schedule)
Why this is a good compromise:
This approach balances:
- Detecting integration problems reasonably early
- Avoiding long waits that slow down development
4. Acceptance Tests
Acceptance tests check whether the software meets business requirements and is ready to be delivered to users.
Purpose:
To confirm the product is ready for customer use.
Why they do not fully fit shift-left:
Acceptance testing is not well suited for a full shift-left strategy.
What can still be shifted left:
Some acceptance-related activities can be moved earlier, such as:
- Defining acceptance criteria early
- Writing user stories early
Why this helps:
-
Improves collaboration between:
- Development teams
- Product owners
- Project stakeholders
Reduces misunderstandings about requirements
Getting early feedback:
Users and stakeholders should be involved earlier in testing to share feedback.
This can include:
- Alpha testing
- Beta testing
- Usability testing
- Early releases
All of this should happen before formal acceptance testing.
In short
Shift-left testing should include:
- Unit tests for fast, automated testing of small code units
- Smoke tests for quick checks of core application health
- Integration tests for validating component interactions (run on a schedule)
-
Acceptance tests mainly at the end, but with:
- Early acceptance criteria
- Early user stories
- Early user and stakeholder feedback
This approach:
- Finds problems earlier
- Improves code quality
- Reduces risk
- Keeps development moving fast without sacrificing reliability
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