diff --git a/helpers/__tests__/editorutils.spec.js b/helpers/__tests__/editorutils.spec.js
new file mode 100644
index 000000000..b0e38e429
--- /dev/null
+++ b/helpers/__tests__/editorutils.spec.js
@@ -0,0 +1,30 @@
+import { getEditorLangForMimeType } from "../editorutils"
+
+describe("getEditorLangForMimeType", () => {
+  test("returns 'json' for valid JSON mimes", () => {
+    expect(getEditorLangForMimeType("application/json")).toMatch("json")
+    expect(getEditorLangForMimeType("application/hal+json")).toMatch("json")
+    expect(getEditorLangForMimeType("application/vnd.api+json")).toMatch("json")
+  })
+
+  test("returns 'xml' for valid XML mimes", () => {
+    expect(getEditorLangForMimeType("application/xml")).toMatch("xml")
+  })
+
+  test("returns 'html' for valid HTML mimes", () => {
+    expect(getEditorLangForMimeType("text/html")).toMatch("html")
+  })
+
+  test("returns 'plain_text' for plain text mime", () => {
+    expect(getEditorLangForMimeType("text/plain")).toMatch("plain_text")
+  })
+
+  test("returns 'plain_text' for unimplemented mimes", () => {
+    expect(getEditorLangForMimeType("image/gif")).toMatch("plain_text")
+  })
+
+  test("returns 'plain_text' for null/undefined mimes", () => {
+    expect(getEditorLangForMimeType(null)).toMatch("plain_text")
+    expect(getEditorLangForMimeType(undefined)).toMatch("plain_text")
+  })
+})