fixing test that would fail due to uncontrolled RNG

Author: Benjin

src/nps/userSurvey.ts

@@ -15,7 +15,9 @@ import { ReactWebviewPanelController } from "../controllers/reactWebviewPanelCon
 import { sendActionEvent } from "../telemetry/telemetry";
 import VscodeWrapper from "../controllers/vscodeWrapper";
 
-const PROBABILITY = 0.15;
+/** Likelihood that a user is prompted to take the survey, after they've already passed all other checks */
+export const SELECTION_PROBABILITY = 0.15;
+
 export const SESSION_COUNT_KEY = "nps/sessionCount";
 export const LAST_SESSION_DATE_KEY = "nps/lastSessionDate";
 export const SKIP_VERSION_KEY = "nps/skipVersion";
@@ -227,7 +229,8 @@ export class UserSurvey {
         }
 
         // 5. Of the remaining users, randomly select a subset to prompt to ensure we get feedback from a variety of users over time
-        const isCandidate = globalState.get(IS_CANDIDATE_KEY, false) || Math.random() < PROBABILITY;
+        const isCandidate =
+            globalState.get(IS_CANDIDATE_KEY, false) || Math.random() < SELECTION_PROBABILITY;
         await globalState.update(IS_CANDIDATE_KEY, isCandidate);
 
         if (!isCandidate) {

test/unit/userSurvey.test.ts

@@ -15,6 +15,7 @@ import { TelemetryActions, TelemetryViews } from "../../src/sharedInterfaces/tel
 import {
     FunnelSteps,
     NEVER_KEY,
+    SELECTION_PROBABILITY,
     SKIP_VERSION_KEY,
     UserSurvey,
     UserSurveyWebviewController,
@@ -289,7 +290,9 @@ suite("UserSurvey Tests", () => {
             globalState.get.withArgs(SKIP_VERSION_KEY, "").returns("");
             globalState.get.withArgs("nps/lastSessionDate").returns("01/01/2023"); // not today
             globalState.get.withArgs("nps/sessionCount").returns(999); // high enough to be eligible
-            globalState.get.withArgs("nps/isCandidate").returns(false); // not selected by die roll
+            globalState.get.withArgs("nps/isCandidate").returns(false); // not already determined to be a candidate
+
+            sinon.stub(Math, "random").returns(SELECTION_PROBABILITY + 0.1); // ensure not selected by RNG check
 
             const userSurvey = UserSurvey.getInstance();
             const result = await userSurvey["shouldPromptForFeedback"](testSurveySource);