AB testing - Ensure test group sizes are rounded down to min resolution if needed#15274
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AB testing - Ensure test group sizes are rounded down to min resolution if needed#15274
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Jakeii
commented
Feb 2, 2026
| getTestGroupName(group), | ||
| group.audienceSize * MVT_COUNT, | ||
| ); | ||
| } else if (currentTestGroup.length !== group.audienceSize * MVT_COUNT) { |
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This check was also missing, it was calling the resizeTestGroup even if a resize wasn't needed, no issue with this other than unnecessary logging.
Jakeii
commented
Feb 2, 2026
| if (!currentTest) { | ||
| console.log(`Adding new test group: ${test.name}:${test.group}`); | ||
| updateTestGroups.forEach((group) => { | ||
| const currentTestGroup = testGroupMVTs.getTestGroup( |
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renamed these vars, they refer to the test group not the test.
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on-ye
approved these changes
Feb 2, 2026
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What does this change?
Ensure that ab test groups sizes do not exceed the overall test size by rounding non-integer groups down.
Why?
If group sizes are rounded up (or used as is) it could cause the actual mvt usage to exceed that of the test e.g.
A 20% test / 3 groups = 6.66666...7
The minimum actual test resolution is 0.1% if rounded up to 6.7% the actual MVT usage would be 20.1% which could cause issues when calculating if there's enough space for a test.
The lack of rounding also caused an issue on test resize as it tries to update an array to a decimal length, which this also fixes.
I've added a test case for this.