diff --git a/params.js b/params.js
index ab7ca5f8..30bbaf85 100644
--- a/params.js
+++ b/params.js
@@ -82,18 +82,36 @@ class Params {
                  this.startDelay = 100;
         }
 
-        for (const paramKey of ["tag", "tags", "test", "tests"]) {
-            this.testList = this._parseTestListParam(sourceParams, paramKey);
-        }
-
-        this.testIterationCount = this._parseIntParam(sourceParams, "iterationCount", 1);
-        this.testWorstCaseCount = this._parseIntParam(sourceParams, "worstCaseCount", 1);
+        this.testList = this._parseOneOf(sourceParams, ["testList", "tag", "tags", "test", "tests"], this._parseTestListParam);
+        this.testIterationCount = this._parseOneOf(sourceParams, ["testIterationCount", "iterationCount", "iterations" ], this._parseIntParam, 1);
+        this.testWorstCaseCount = this._parseOneOf(sourceParams, ["testWorstCaseCount", "worstCaseCount", "worst"], this._parseIntParam, 1);
 
         const unused = Array.from(sourceParams.keys());
         if (unused.length > 0)
             console.error("Got unused source params", unused);
     }
 
+    _parseOneOf(sourceParams, paramKeys, parseFunction, ...args) {
+        const defaultParamKey = paramKeys[0]
+        let result = undefined;
+        let parsedParamKey = undefined;
+        for (const paramKey of paramKeys) {
+            if (!sourceParams.has(paramKey)) {
+                continue;
+            }
+            const parseResult = parseFunction.call(this, sourceParams, paramKey, ...args);
+            if (parsedParamKey) {
+                throw new Error(`Cannot parse ${paramKey}, overriding previous "${parsedParamKey}" value ${JSON.stringify(result)} with ${JSON.stringify(parseResult)}`)
+            }
+            parsedParamKey = paramKey;
+            result = parseResult;
+        }
+        if (!parsedParamKey) {
+            return DefaultJetStreamParams[defaultParamKey];
+        }
+        return result;
+    }
+
     _parseTestListParam(sourceParams, key) {
         if (!sourceParams.has(key))
             return this.testList;
@@ -108,9 +126,6 @@ class Params {
         }
         testList = testList.map(each => each.trim());
         sourceParams.delete(key);
-        if (this.testList.length > 0 && testList.length > 0) {
-            throw new Error(`Overriding previous testList='${this.testList.join()}' with ${key} url-parameter.`);
-        }
         return testList;
     }
 
diff --git a/tests/unit-tests.js b/tests/unit-tests.js
index ac5d5e12..c695556b 100644
--- a/tests/unit-tests.js
+++ b/tests/unit-tests.js
@@ -28,7 +28,7 @@ function assertThrows(message, func) {
   } catch (e) {
     didThrow = true;
   }
-  assertTrue(didThrow, message);
+  assertTrue(didThrow, `Test did not throw: ${message}`);
 }
 
 (function testTagsAreLowerCaseStrings() {
@@ -276,3 +276,20 @@ async function testStartupBenchmarkInnerTests() {
     }
   );
 })();
+
+
+(function testParseIterationCount() {
+  assertThrows("Cannot parse negative iterationCounts", 
+    () => {
+      const sourceParams = new Map(Object.entries({ iterationCount: -123, }));
+      new Params(sourceParams);
+    });
+  assertThrows("Cannot parse multiple iterationCounts", 
+    () => {
+      const sourceParams = new Map(Object.entries({ iterationCount: 123, testIterationCount: 10 }));
+      new Params(sourceParams);
+    });
+  let sourceParams = new Map(Object.entries({ iterationCount: 123 }));
+  let params = new Params(sourceParams);
+  assertEquals(params.testIterationCount, 123);
+})();