diff --git a/tests/util/source-maps.js b/tests/util/source-maps.js
index 8a1ee227085c..695ba91f6af7 100644
--- a/tests/util/source-maps.js
+++ b/tests/util/source-maps.js
@@ -27,15 +27,10 @@ export function parseSourceMaps(result) {
  */
 function annotatedMappings(map) {
   const smc = new SourceMapConsumer(map)
-  const annotations = []
-
-  const lineAnnotations = {}
+  const annotations = {}
 
   smc.eachMapping((mapping) => {
-    // For each generated line:
-    // Find the first and last columns
-    // And join the line/column numbers from the original source for those
-    lineAnnotations[mapping.generatedLine] = lineAnnotations[mapping.generatedLine] || {
+    let annotation = (annotations[mapping.generatedLine] = annotations[mapping.generatedLine] || {
       ...mapping,
 
       original: {
@@ -47,39 +42,38 @@ function annotatedMappings(map) {
         start: [mapping.generatedLine, mapping.generatedColumn],
         end: [mapping.generatedLine, mapping.generatedColumn],
       },
-    }
-
-    let annotation = lineAnnotations[mapping.generatedLine]
+    })
 
     annotation.generated.end[0] = mapping.generatedLine
     annotation.generated.end[1] = mapping.generatedColumn
 
     annotation.original.end[0] = mapping.originalLine
     annotation.original.end[1] = mapping.originalColumn
-
-    annotations.push(
-      `${mapping.originalLine}:${mapping.originalColumn} -> ${mapping.generatedLine}:${mapping.generatedColumn}`
-    )
   })
 
-  /**
-   * @param {object} range
-   * @param {[number, number]} range.start
-   * @param {[number, number]} range.end
-   */
-  function format(range) {
-    if (range.start[0] === range.end[0]) {
-      if (range.start[1] === range.end[1]) {
-        return `${range.start[0]}:${range.start[1]}`
-      }
+  return Object.values(annotations).map((annotation) => {
+    return `${formatRange(annotation.original)} -> ${formatRange(annotation.generated)}`
+  })
+}
 
-      return `${range.start[0]}:${range.start[1]}-${range.end[1]}`
+/**
+ * @param {object} range
+ * @param {[number, number]} range.start
+ * @param {[number, number]} range.end
+ */
+function formatRange(range) {
+  if (range.start[0] === range.end[0]) {
+    // This range is on the same line
+    // and the columns are the same
+    if (range.start[1] === range.end[1]) {
+      return `${range.start[0]}:${range.start[1]}`
     }
 
-    return `${range.start[0]}:${range.start[1]}-${range.end[0]}:${range.end[1]}`
+    // This range is on the same line
+    // but the columns are different
+    return `${range.start[0]}:${range.start[1]}-${range.end[1]}`
   }
 
-  return Object.values(lineAnnotations).map((annotation) => {
-    return `${format(annotation.original)} -> ${format(annotation.generated)}`
-  })
+  // This range spans multiple lines
+  return `${range.start[0]}:${range.start[1]}-${range.end[0]}:${range.end[1]}`
 }