add diff exp test class

client/src/components/geneExpression/geneSet.js

@@ -100,6 +100,10 @@ class GeneSet extends React.Component {
     const { isOpen } = this.state;
     const genesetNameLengthVisible = 150; /* this magic number determines how much of a long geneset name we see */
     const genesetIsEmpty = setGenes.length === 0;
+    let testClass = "geneset-expand";
+
+    if (setName.contains("pop1High")) testClass = "pop-1-geneset-expand";
+    else if (setName.contains("pop2High")) testClass = "pop-2-geneset-expand";
 
     return (
       <div style={{ marginBottom: 3 }}>
@@ -113,7 +117,7 @@ class GeneSet extends React.Component {
           <span
             role="menuitem"
             tabIndex="0"
-            data-testclass="geneset-expand"
+            data-testclass={testClass}
             data-testid={`${setName}:geneset-expand`}
             onKeyPress={
               /* TODO(colinmegill): #2101: click handler on span */ () => {}