diff --git a/lib/dependency-caching.js b/lib/dependency-caching.js
index 7f9e6adec..78db36271 100644
--- a/lib/dependency-caching.js
+++ b/lib/dependency-caching.js
@@ -31,6 +31,7 @@ const actionsCache = __importStar(require("@actions/cache"));
 const glob = __importStar(require("@actions/glob"));
 const caching_utils_1 = require("./caching-utils");
 const util_1 = require("./util");
+const environment_1 = require("./environment");
 const CODEQL_DEPENDENCY_CACHE_PREFIX = "codeql-dependencies";
 const CODEQL_DEPENDENCY_CACHE_VERSION = 1;
 /**
@@ -155,6 +156,11 @@ async function cacheKey(language, cacheConfig) {
  */
 async function cachePrefix(language) {
     const runnerOs = (0, util_1.getRequiredEnvParam)("RUNNER_OS");
-    return `${CODEQL_DEPENDENCY_CACHE_PREFIX}-${CODEQL_DEPENDENCY_CACHE_VERSION}-${runnerOs}-${language}-`;
+    const customPrefix = process.env[environment_1.EnvVar.DEPENDENCY_CACHING_PREFIX];
+    let prefix = CODEQL_DEPENDENCY_CACHE_PREFIX;
+    if (customPrefix !== undefined && customPrefix.length > 0) {
+        prefix = `${prefix}-${customPrefix}`;
+    }
+    return `${prefix}-${CODEQL_DEPENDENCY_CACHE_VERSION}-${runnerOs}-${language}-`;
 }
 //# sourceMappingURL=dependency-caching.js.map
\ No newline at end of file
diff --git a/lib/dependency-caching.js.map b/lib/dependency-caching.js.map
index c42ee9f7f..a0f438a74 100644
--- a/lib/dependency-caching.js.map
+++ b/lib/dependency-caching.js.map
@@ -1 +1 @@
-{"version":3,"file":"dependency-caching.js","sourceRoot":"","sources":["../src/dependency-caching.ts"],"names":[],"mappings":";;;;;;;;;;;;;;;;;;;;;;;;;AA4EA,4DAiDC;AAQD,wDAwCC;AA7KD,uCAAyB;AACzB,+BAA4B;AAE5B,6DAA+C;AAC/C,oDAAsC;AAEtC,mDAAoD;AAIpD,iCAA6C;AAgB7C,MAAM,8BAA8B,GAAG,qBAAqB,CAAC;AAC7D,MAAM,+BAA+B,GAAG,CAAC,CAAC;AAE1C;;GAEG;AACH,MAAM,2BAA2B,GAAwC;IACvE,IAAI,EAAE;QACJ,KAAK,EAAE;YACL,QAAQ;YACR,IAAA,WAAI,EAAC,EAAE,CAAC,OAAO,EAAE,EAAE,KAAK,EAAE,YAAY,CAAC;YACvC,SAAS;YACT,IAAA,WAAI,EAAC,EAAE,CAAC,OAAO,EAAE,EAAE,SAAS,EAAE,QAAQ,CAAC;SACxC;QACD,IAAI,EAAE;YACJ,QAAQ;YACR,YAAY;YACZ,SAAS;YACT,cAAc;YACd,8BAA8B;YAC9B,yBAAyB;YACzB,6BAA6B;YAC7B,wBAAwB;YACxB,wBAAwB;SACzB;KACF;IACD,MAAM,EAAE;QACN,KAAK,EAAE,CAAC,IAAA,WAAI,EAAC,EAAE,CAAC,OAAO,EAAE,EAAE,QAAQ,EAAE,UAAU,CAAC,CAAC;QACjD,IAAI,EAAE;YACJ,QAAQ;YACR,uBAAuB;SACxB;KACF;IACD,EAAE,EAAE;QACF,KAAK,EAAE,CAAC,IAAA,WAAI,EAAC,EAAE,CAAC,OAAO,EAAE,EAAE,IAAI,EAAE,KAAK,EAAE,KAAK,CAAC,CAAC;QAC/C,IAAI,EAAE,CAAC,WAAW,CAAC;KACpB;CACF,CAAC;AAEF,KAAK,UAAU,WAAW,CAAC,QAAkB;IAC3C,OAAO,IAAI,CAAC,MAAM,CAAC,QAAQ,CAAC,IAAI,CAAC,IAAI,CAAC,CAAC,CAAC;AAC1C,CAAC;AAED;;;;;;GAMG;AACI,KAAK,UAAU,wBAAwB,CAC5C,SAAqB,EACrB,MAAc;IAEd,MAAM,cAAc,GAAe,EAAE,CAAC;IAEtC,KAAK,MAAM,QAAQ,IAAI,SAAS,EAAE,CAAC;QACjC,MAAM,WAAW,GAAG,2BAA2B,CAAC,QAAQ,CAAC,CAAC;QAE1D,IAAI,WAAW,KAAK,SAAS,EAAE,CAAC;YAC9B,MAAM,CAAC,IAAI,CACT,6CAA6C,QAAQ,8CAA8C,CACpG,CAAC;YACF,SAAS;QACX,CAAC;QAED,gGAAgG;QAChG,wBAAwB;QACxB,MAAM,OAAO,GAAG,MAAM,WAAW,CAAC,WAAW,CAAC,IAAI,CAAC,CAAC;QAEpD,IAAI,CAAC,MAAM,OAAO,CAAC,IAAI,EAAE,CAAC,CAAC,MAAM,KAAK,CAAC,EAAE,CAAC;YACxC,MAAM,CAAC,IAAI,CACT,6CAA6C,QAAQ,mDAAmD,CACzG,CAAC;YACF,SAAS;QACX,CAAC;QAED,MAAM,UAAU,GAAG,MAAM,QAAQ,CAAC,QAAQ,EAAE,WAAW,CAAC,CAAC;QACzD,MAAM,WAAW,GAAa,CAAC,MAAM,WAAW,CAAC,QAAQ,CAAC,CAAC,CAAC;QAE5D,MAAM,CAAC,IAAI,CACT,yBAAyB,QAAQ,aAAa,UAAU,qBAAqB,WAAW,CAAC,IAAI,CAC3F,IAAI,CACL,EAAE,CACJ,CAAC;QAEF,MAAM,MAAM,GAAG,MAAM,YAAY,CAAC,YAAY,CAC5C,WAAW,CAAC,KAAK,EACjB,UAAU,EACV,WAAW,CACZ,CAAC;QAEF,IAAI,MAAM,KAAK,SAAS,EAAE,CAAC;YACzB,MAAM,CAAC,IAAI,CAAC,oBAAoB,MAAM,QAAQ,QAAQ,GAAG,CAAC,CAAC;YAC3D,cAAc,CAAC,IAAI,CAAC,QAAQ,CAAC,CAAC;QAChC,CAAC;IACH,CAAC;IAED,OAAO,cAAc,CAAC;AACxB,CAAC;AAED;;;;;GAKG;AACI,KAAK,UAAU,sBAAsB,CAAC,MAAc,EAAE,MAAc;IACzE,KAAK,MAAM,QAAQ,IAAI,MAAM,CAAC,SAAS,EAAE,CAAC;QACxC,MAAM,WAAW,GAAG,2BAA2B,CAAC,QAAQ,CAAC,CAAC;QAE1D,IAAI,WAAW,KAAK,SAAS,EAAE,CAAC;YAC9B,MAAM,CAAC,IAAI,CACT,2CAA2C,QAAQ,8CAA8C,CAClG,CAAC;YACF,SAAS;QACX,CAAC;QAED,gGAAgG;QAChG,wBAAwB;QACxB,MAAM,OAAO,GAAG,MAAM,WAAW,CAAC,WAAW,CAAC,IAAI,CAAC,CAAC;QAEpD,IAAI,CAAC,MAAM,OAAO,CAAC,IAAI,EAAE,CAAC,CAAC,MAAM,KAAK,CAAC,EAAE,CAAC;YACxC,MAAM,CAAC,IAAI,CACT,2CAA2C,QAAQ,mDAAmD,CACvG,CAAC;YACF,SAAS;QACX,CAAC;QAED,MAAM,IAAI,GAAG,MAAM,IAAA,iCAAiB,EAAC,WAAW,CAAC,KAAK,EAAE,MAAM,CAAC,CAAC;QAEhE,iCAAiC;QACjC,IAAI,IAAI,KAAK,CAAC,EAAE,CAAC;YACf,MAAM,CAAC,IAAI,CACT,2CAA2C,QAAQ,qBAAqB,CACzE,CAAC;YACF,SAAS;QACX,CAAC;QAED,MAAM,GAAG,GAAG,MAAM,QAAQ,CAAC,QAAQ,EAAE,WAAW,CAAC,CAAC;QAElD,MAAM,CAAC,IAAI,CACT,2BAA2B,IAAI,QAAQ,QAAQ,aAAa,GAAG,EAAE,CAClE,CAAC;QAEF,MAAM,YAAY,CAAC,SAAS,CAAC,WAAW,CAAC,KAAK,EAAE,GAAG,CAAC,CAAC;IACvD,CAAC;AACH,CAAC;AAED;;;;;;GAMG;AACH,KAAK,UAAU,QAAQ,CACrB,QAAkB,EAClB,WAAwB;IAExB,MAAM,IAAI,GAAG,MAAM,IAAI,CAAC,SAAS,CAAC,WAAW,CAAC,IAAI,CAAC,IAAI,CAAC,IAAI,CAAC,CAAC,CAAC;IAC/D,OAAO,GAAG,MAAM,WAAW,CAAC,QAAQ,CAAC,GAAG,IAAI,EAAE,CAAC;AACjD,CAAC;AAED;;;;;;GAMG;AACH,KAAK,UAAU,WAAW,CAAC,QAAkB;IAC3C,MAAM,QAAQ,GAAG,IAAA,0BAAmB,EAAC,WAAW,CAAC,CAAC;IAClD,OAAO,GAAG,8BAA8B,IAAI,+BAA+B,IAAI,QAAQ,IAAI,QAAQ,GAAG,CAAC;AACzG,CAAC"}
\ No newline at end of file
+{"version":3,"file":"dependency-caching.js","sourceRoot":"","sources":["../src/dependency-caching.ts"],"names":[],"mappings":";;;;;;;;;;;;;;;;;;;;;;;;;AA6EA,4DAiDC;AAQD,wDAwCC;AA9KD,uCAAyB;AACzB,+BAA4B;AAE5B,6DAA+C;AAC/C,oDAAsC;AAEtC,mDAAoD;AAIpD,iCAA6C;AAC7C,+CAAuC;AAgBvC,MAAM,8BAA8B,GAAG,qBAAqB,CAAC;AAC7D,MAAM,+BAA+B,GAAG,CAAC,CAAC;AAE1C;;GAEG;AACH,MAAM,2BAA2B,GAAwC;IACvE,IAAI,EAAE;QACJ,KAAK,EAAE;YACL,QAAQ;YACR,IAAA,WAAI,EAAC,EAAE,CAAC,OAAO,EAAE,EAAE,KAAK,EAAE,YAAY,CAAC;YACvC,SAAS;YACT,IAAA,WAAI,EAAC,EAAE,CAAC,OAAO,EAAE,EAAE,SAAS,EAAE,QAAQ,CAAC;SACxC;QACD,IAAI,EAAE;YACJ,QAAQ;YACR,YAAY;YACZ,SAAS;YACT,cAAc;YACd,8BAA8B;YAC9B,yBAAyB;YACzB,6BAA6B;YAC7B,wBAAwB;YACxB,wBAAwB;SACzB;KACF;IACD,MAAM,EAAE;QACN,KAAK,EAAE,CAAC,IAAA,WAAI,EAAC,EAAE,CAAC,OAAO,EAAE,EAAE,QAAQ,EAAE,UAAU,CAAC,CAAC;QACjD,IAAI,EAAE;YACJ,QAAQ;YACR,uBAAuB;SACxB;KACF;IACD,EAAE,EAAE;QACF,KAAK,EAAE,CAAC,IAAA,WAAI,EAAC,EAAE,CAAC,OAAO,EAAE,EAAE,IAAI,EAAE,KAAK,EAAE,KAAK,CAAC,CAAC;QAC/C,IAAI,EAAE,CAAC,WAAW,CAAC;KACpB;CACF,CAAC;AAEF,KAAK,UAAU,WAAW,CAAC,QAAkB;IAC3C,OAAO,IAAI,CAAC,MAAM,CAAC,QAAQ,CAAC,IAAI,CAAC,IAAI,CAAC,CAAC,CAAC;AAC1C,CAAC;AAED;;;;;;GAMG;AACI,KAAK,UAAU,wBAAwB,CAC5C,SAAqB,EACrB,MAAc;IAEd,MAAM,cAAc,GAAe,EAAE,CAAC;IAEtC,KAAK,MAAM,QAAQ,IAAI,SAAS,EAAE,CAAC;QACjC,MAAM,WAAW,GAAG,2BAA2B,CAAC,QAAQ,CAAC,CAAC;QAE1D,IAAI,WAAW,KAAK,SAAS,EAAE,CAAC;YAC9B,MAAM,CAAC,IAAI,CACT,6CAA6C,QAAQ,8CAA8C,CACpG,CAAC;YACF,SAAS;QACX,CAAC;QAED,gGAAgG;QAChG,wBAAwB;QACxB,MAAM,OAAO,GAAG,MAAM,WAAW,CAAC,WAAW,CAAC,IAAI,CAAC,CAAC;QAEpD,IAAI,CAAC,MAAM,OAAO,CAAC,IAAI,EAAE,CAAC,CAAC,MAAM,KAAK,CAAC,EAAE,CAAC;YACxC,MAAM,CAAC,IAAI,CACT,6CAA6C,QAAQ,mDAAmD,CACzG,CAAC;YACF,SAAS;QACX,CAAC;QAED,MAAM,UAAU,GAAG,MAAM,QAAQ,CAAC,QAAQ,EAAE,WAAW,CAAC,CAAC;QACzD,MAAM,WAAW,GAAa,CAAC,MAAM,WAAW,CAAC,QAAQ,CAAC,CAAC,CAAC;QAE5D,MAAM,CAAC,IAAI,CACT,yBAAyB,QAAQ,aAAa,UAAU,qBAAqB,WAAW,CAAC,IAAI,CAC3F,IAAI,CACL,EAAE,CACJ,CAAC;QAEF,MAAM,MAAM,GAAG,MAAM,YAAY,CAAC,YAAY,CAC5C,WAAW,CAAC,KAAK,EACjB,UAAU,EACV,WAAW,CACZ,CAAC;QAEF,IAAI,MAAM,KAAK,SAAS,EAAE,CAAC;YACzB,MAAM,CAAC,IAAI,CAAC,oBAAoB,MAAM,QAAQ,QAAQ,GAAG,CAAC,CAAC;YAC3D,cAAc,CAAC,IAAI,CAAC,QAAQ,CAAC,CAAC;QAChC,CAAC;IACH,CAAC;IAED,OAAO,cAAc,CAAC;AACxB,CAAC;AAED;;;;;GAKG;AACI,KAAK,UAAU,sBAAsB,CAAC,MAAc,EAAE,MAAc;IACzE,KAAK,MAAM,QAAQ,IAAI,MAAM,CAAC,SAAS,EAAE,CAAC;QACxC,MAAM,WAAW,GAAG,2BAA2B,CAAC,QAAQ,CAAC,CAAC;QAE1D,IAAI,WAAW,KAAK,SAAS,EAAE,CAAC;YAC9B,MAAM,CAAC,IAAI,CACT,2CAA2C,QAAQ,8CAA8C,CAClG,CAAC;YACF,SAAS;QACX,CAAC;QAED,gGAAgG;QAChG,wBAAwB;QACxB,MAAM,OAAO,GAAG,MAAM,WAAW,CAAC,WAAW,CAAC,IAAI,CAAC,CAAC;QAEpD,IAAI,CAAC,MAAM,OAAO,CAAC,IAAI,EAAE,CAAC,CAAC,MAAM,KAAK,CAAC,EAAE,CAAC;YACxC,MAAM,CAAC,IAAI,CACT,2CAA2C,QAAQ,mDAAmD,CACvG,CAAC;YACF,SAAS;QACX,CAAC;QAED,MAAM,IAAI,GAAG,MAAM,IAAA,iCAAiB,EAAC,WAAW,CAAC,KAAK,EAAE,MAAM,CAAC,CAAC;QAEhE,iCAAiC;QACjC,IAAI,IAAI,KAAK,CAAC,EAAE,CAAC;YACf,MAAM,CAAC,IAAI,CACT,2CAA2C,QAAQ,qBAAqB,CACzE,CAAC;YACF,SAAS;QACX,CAAC;QAED,MAAM,GAAG,GAAG,MAAM,QAAQ,CAAC,QAAQ,EAAE,WAAW,CAAC,CAAC;QAElD,MAAM,CAAC,IAAI,CACT,2BAA2B,IAAI,QAAQ,QAAQ,aAAa,GAAG,EAAE,CAClE,CAAC;QAEF,MAAM,YAAY,CAAC,SAAS,CAAC,WAAW,CAAC,KAAK,EAAE,GAAG,CAAC,CAAC;IACvD,CAAC;AACH,CAAC;AAED;;;;;;GAMG;AACH,KAAK,UAAU,QAAQ,CACrB,QAAkB,EAClB,WAAwB;IAExB,MAAM,IAAI,GAAG,MAAM,IAAI,CAAC,SAAS,CAAC,WAAW,CAAC,IAAI,CAAC,IAAI,CAAC,IAAI,CAAC,CAAC,CAAC;IAC/D,OAAO,GAAG,MAAM,WAAW,CAAC,QAAQ,CAAC,GAAG,IAAI,EAAE,CAAC;AACjD,CAAC;AAED;;;;;;GAMG;AACH,KAAK,UAAU,WAAW,CAAC,QAAkB;IAC3C,MAAM,QAAQ,GAAG,IAAA,0BAAmB,EAAC,WAAW,CAAC,CAAC;IAClD,MAAM,YAAY,GAAG,OAAO,CAAC,GAAG,CAAC,oBAAM,CAAC,yBAAyB,CAAC,CAAC;IACnE,IAAI,MAAM,GAAG,8BAA8B,CAAC;IAE5C,IAAI,YAAY,KAAK,SAAS,IAAI,YAAY,CAAC,MAAM,GAAG,CAAC,EAAE,CAAC;QAC1D,MAAM,GAAG,GAAG,MAAM,IAAI,YAAY,EAAE,CAAC;IACvC,CAAC;IAED,OAAO,GAAG,MAAM,IAAI,+BAA+B,IAAI,QAAQ,IAAI,QAAQ,GAAG,CAAC;AACjF,CAAC"}
\ No newline at end of file
diff --git a/lib/environment.js b/lib/environment.js
index 6e27a2ecf..66a28a9a4 100644
--- a/lib/environment.js
+++ b/lib/environment.js
@@ -86,5 +86,10 @@ var EnvVar;
      * change the inputs to the Action.
      */
     EnvVar["DEPENDENCY_CACHING"] = "CODEQL_ACTION_DEPENDENCY_CACHING";
+    /**
+     * An optional string to add into the cache key used by dependency caching.
+     * Useful for testing purposes where multiple caches may be stored in the same repository.
+     */
+    EnvVar["DEPENDENCY_CACHING_PREFIX"] = "CODEQL_ACTION_DEPENDENCY_CACHE_PREFIX";
 })(EnvVar || (exports.EnvVar = EnvVar = {}));
 //# sourceMappingURL=environment.js.map
\ No newline at end of file
diff --git a/lib/environment.js.map b/lib/environment.js.map
index 4925b1cdd..fb75e58cc 100644
--- a/lib/environment.js.map
+++ b/lib/environment.js.map
@@ -1 +1 @@
-{"version":3,"file":"environment.js","sourceRoot":"","sources":["../src/environment.ts"],"names":[],"mappings":";;;AAAA;;;;;GAKG;AACH,IAAY,MAqGX;AArGD,WAAY,MAAM;IAChB,2DAA2D;IAC3D,+FAAqF,CAAA;IAErF,6DAA6D;IAC7D,mGAAyF,CAAA;IAEzF;;;OAGG;IACH,4CAAkC,CAAA;IAElC,gEAAgE;IAChE,qEAA2D,CAAA;IAE3D;;;OAGG;IACH,yFAA+E,CAAA;IAE/E;;;OAGG;IACH,yEAA+D,CAAA;IAE/D,gFAAgF;IAChF,6DAAmD,CAAA;IAEnD;;;OAGG;IACH,uEAA6D,CAAA;IAE7D,gEAAgE;IAChE,mEAAyD,CAAA;IAEzD,kFAAkF;IAClF,mFAAyE,CAAA;IAEzE,4CAA4C;IAC5C,4DAAkD,CAAA;IAElD;;;OAGG;IACH,yDAA+C,CAAA;IAE/C,6CAA6C;IAC7C,uCAA6B,CAAA;IAE7B,+EAA+E;IAC/E,iDAAuC,CAAA;IAEvC,mEAAyD,CAAA;IAEzD,8DAA8D;IAC9D,6EAAmE,CAAA;IAEnE;;;OAGG;IACH,2FAAiF,CAAA;IAEjF,mFAAmF;IACnF,6FAAmF,CAAA;IAEnF,qFAAqF;IACrF,+CAAqC,CAAA;IAErC,mEAAyD,CAAA;IAEzD,kEAAkE;IAClE,2CAAiC,CAAA;IAEjC;;;;;;OAMG;IACH,4DAAkD,CAAA;IAElD;;;OAGG;IACH,wDAA8C,CAAA;IAE9C;;;;OAIG;IACH,iEAAuD,CAAA;AACzD,CAAC,EArGW,MAAM,sBAAN,MAAM,QAqGjB"}
\ No newline at end of file
+{"version":3,"file":"environment.js","sourceRoot":"","sources":["../src/environment.ts"],"names":[],"mappings":";;;AAAA;;;;;GAKG;AACH,IAAY,MA2GX;AA3GD,WAAY,MAAM;IAChB,2DAA2D;IAC3D,+FAAqF,CAAA;IAErF,6DAA6D;IAC7D,mGAAyF,CAAA;IAEzF;;;OAGG;IACH,4CAAkC,CAAA;IAElC,gEAAgE;IAChE,qEAA2D,CAAA;IAE3D;;;OAGG;IACH,yFAA+E,CAAA;IAE/E;;;OAGG;IACH,yEAA+D,CAAA;IAE/D,gFAAgF;IAChF,6DAAmD,CAAA;IAEnD;;;OAGG;IACH,uEAA6D,CAAA;IAE7D,gEAAgE;IAChE,mEAAyD,CAAA;IAEzD,kFAAkF;IAClF,mFAAyE,CAAA;IAEzE,4CAA4C;IAC5C,4DAAkD,CAAA;IAElD;;;OAGG;IACH,yDAA+C,CAAA;IAE/C,6CAA6C;IAC7C,uCAA6B,CAAA;IAE7B,+EAA+E;IAC/E,iDAAuC,CAAA;IAEvC,mEAAyD,CAAA;IAEzD,8DAA8D;IAC9D,6EAAmE,CAAA;IAEnE;;;OAGG;IACH,2FAAiF,CAAA;IAEjF,mFAAmF;IACnF,6FAAmF,CAAA;IAEnF,qFAAqF;IACrF,+CAAqC,CAAA;IAErC,mEAAyD,CAAA;IAEzD,kEAAkE;IAClE,2CAAiC,CAAA;IAEjC;;;;;;OAMG;IACH,4DAAkD,CAAA;IAElD;;;OAGG;IACH,wDAA8C,CAAA;IAE9C;;;;OAIG;IACH,iEAAuD,CAAA;IAEvD;;;OAGG;IACH,6EAAmE,CAAA;AACrE,CAAC,EA3GW,MAAM,sBAAN,MAAM,QA2GjB"}
\ No newline at end of file
diff --git a/src/dependency-caching.ts b/src/dependency-caching.ts
index 5de3e0251..389b7e655 100644
--- a/src/dependency-caching.ts
+++ b/src/dependency-caching.ts
@@ -9,6 +9,7 @@ import { Config } from "./config-utils";
 import { Language } from "./languages";
 import { Logger } from "./logging";
 import { getRequiredEnvParam } from "./util";
+import { EnvVar } from "./environment";
 
 /**
  * Caching configuration for a particular language.
@@ -197,5 +198,12 @@ async function cacheKey(
  */
 async function cachePrefix(language: Language): Promise<string> {
   const runnerOs = getRequiredEnvParam("RUNNER_OS");
-  return `${CODEQL_DEPENDENCY_CACHE_PREFIX}-${CODEQL_DEPENDENCY_CACHE_VERSION}-${runnerOs}-${language}-`;
+  const customPrefix = process.env[EnvVar.DEPENDENCY_CACHING_PREFIX];
+  let prefix = CODEQL_DEPENDENCY_CACHE_PREFIX;
+
+  if (customPrefix !== undefined && customPrefix.length > 0) {
+    prefix = `${prefix}-${customPrefix}`;
+  }
+
+  return `${prefix}-${CODEQL_DEPENDENCY_CACHE_VERSION}-${runnerOs}-${language}-`;
 }
diff --git a/src/environment.ts b/src/environment.ts
index 9659208de..3431be731 100644
--- a/src/environment.ts
+++ b/src/environment.ts
@@ -105,4 +105,10 @@ export enum EnvVar {
    * change the inputs to the Action.
    */
   DEPENDENCY_CACHING = "CODEQL_ACTION_DEPENDENCY_CACHING",
+
+  /**
+   * An optional string to add into the cache key used by dependency caching.
+   * Useful for testing purposes where multiple caches may be stored in the same repository.
+   */
+  DEPENDENCY_CACHING_PREFIX = "CODEQL_ACTION_DEPENDENCY_CACHE_PREFIX",
 }