return storedVariation if we have one (#6904)

client/lib/abtest/README.md

@@ -26,7 +26,7 @@ module.exports = {
 
 You should include the following information:
 
-* `datestamp` - The YYYMMDD date you want to start tracking the results of the test. If you deploy to production prior to this date, the `abtest` function (see below) will return the value you set for `defaultVariation` and won't track the results.
+* `datestamp` - The YYYMMDD date you want to start tracking the results of the test. If you deploy to production prior to this date, the `abtest` function (see below) will return the any stored variation (which makes for easier testing) or the value you set for `defaultVariation` and won't track the results.
 * `variations` - An object where the keys are the variation names and the values are the allocations. The variation names should be descriptive (don't use `variationA`, `original`, etc). The allocations (50/50) are how you want those variations to be allocated to users. For example, you could also do 90/10 if you want one variation to be shown to only 10% of users. 90/10 is the same as 9/1. If you had three variations you could do 1/1/1 to show each variation one third of the time.
 * `defaultVariation` - The variation to assign users who are not eligible to participate in the test. See the "Dealing with ineligible users" section below for more information.
 

client/lib/abtest/index.js

@@ -110,7 +110,7 @@ ABTest.prototype.getVariationAndSetAsNeeded = function() {
 
 	if ( ! this.hasTestStartedYet() ) {
 		debug( '%s: Test will start on %s.', this.experimentId, this.datestamp );
-		return this.defaultVariation;
+		return savedVariation || this.defaultVariation;
 	}
 
 	if ( savedVariation && includes( this.variationNames, savedVariation ) ) {