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Compare tests

To find regressions, you can compare data from multiple test runs. k6 Cloud provides three graphical ways to compare tests over time:

  • Between a recent run and a baseline
  • Between two selected runs
  • Across all runs for a certain script

Test comparison works only on runs from the same test script

You can't compare two different test scripts.

Use a test as a baseline

Comparing results against a known baseline is a core part of the general methodology for automated performance testing. Baseline tests are important for comparing against a control and finding differences.

Baseline tests should produce enough load to contain meaningful data and ideal results. In other words, a heavy stress test isn't a good baseline. Think much smaller.

To set your baseline, follow these steps:

  1. Open the results for the test run you wish to be your baseline.
  2. Select the three dots in the top right corner, then set as Baseline.

Baseline tests are exempt from data-retention policies.

k6 Cloud Results: Set a baseline

Select test runs to compare

To compare two test runs, follow these steps:

  1. Open up a test run.
  2. In the top right, select Compare result.
  3. Select the test run you want to compare the test to.

k6 Cloud Results: Select test run for comparison

Test comparison mode

When you compare tests, the layout of the performance-overview section changes to comparison mode. Comparison mode has controls for changing base and target tests, and the overview chart now renders time series for the two compared test runs.

Solid lines represent the base run, and dashed lines represent the comparison. To make a certain time series more visible, select the appropriate element in the interactive legend.

k6 Cloud Results: Performance overview comparison

Compare scenarios

If a test has multiple scenarios, k6 presents a performance overview for each one. If the test script uses multiple protocols, k6 categorizes the overview data by protocol.

k6 Cloud Results: Performance overview comparison

Compare thresholds

To compare thresholds, select the Thresholds tab. You can add additional data to the table for the base and target test runs.

You can compare the following threshold data from the current and previous runs:

  • The value of the threshold
  • pass/fail statuses
  • Previous and current test-run values for each threshold and its pass/fail status.

To display a separate threshold chart for each test run, select a threshold.

k6 Cloud Results: Thresholds comparison

Compare checks

To compare checks, use the Checks tab. Here, k6 provides extra data on the table for the base and target test runs.

You can compare the following metrics from the current and previous runs:

  • Success Rate
  • Success Count
  • Fail Count

To display separate check charts for each test run, select a check.

k6 Cloud Results: Checks comparison

Compare HTTP requests

To compare HTTP requests, use the HTTP tab. Here, k6 provides extra data on the table for the base and target test runs.

You can compare the following data from the current and previous runs:

  • Metrics such as:
    • request count
    • avg
    • p95 response time
  • Other data for individual HTTP requests.

To show separate charts, select the rows for each test run that you want to compare. You can add extra charts, such as timing breakdowns for each HTTP request.

k6 Cloud Results: HTTP comparison

To compare runs for a test across time, use the performance-trending chart. The chart displays test-run metrics, using colors to signal the status of a specific run.

To view the performance-trending chart for multiple tests that belong to the same project, open the Project page:

Project Performance Trending

Additionally, to view the performance-trending chart for an individual test, open the test's page:

Test Performance Trending

This last chart shows more data points over time. For more information about an individual run, hover over any bar in the chart.

By default, the data displayed in the performance-trending chart is the p95 of the HTTP response time (http_req_time).

The chart displays a summary trending metric, an aggregated value for all metric data points in the test run. k6 produces a single value for each test run using the trending metric, and then plots each value the chart. You can customize the trending metric on a per-test basis.

To customize the trending metric used for a test:

  1. Navigate to the Project page.
  2. Select the three dots at the top-right corner of the test's performance-trending chart.
  3. Select Trending metric.

Customizing Trending Metric Step 1

This brings up a window:

Customizing Trending Metric Step 2

From the window, you can select the metric to use in the performance-trending chart. Note that both standard (created by all k6 test runs) and custom (user-defined) metrics are listed. This example selects CPU Usage:

Customizing Trending Metric Step 3

After you select a metric, you can select:

  • The aggregation function to apply to the metric (in this case, "Average" is selected).
  • A set of tags & tag values used to filter the metric's values (in this case, selecting values only from instances in the amazon:us:ashburn load zone).

To reset the configuration, use the default trending metric with Reset to default trending metric.

After you select the desired parameters, Save to apply the changes. k6 calculates the required values, then plots them in the performance-trending chart. In this example, the results look like this:

Customizing Trending Metric Step 4