diff --git a/browser/components/extensions/test/xpcshell/test_ext_settings_overrides_search.js b/browser/components/extensions/test/xpcshell/test_ext_settings_overrides_search.js
index 141bf7af58b5..9276fbaf3655 100644
--- a/browser/components/extensions/test/xpcshell/test_ext_settings_overrides_search.js
+++ b/browser/components/extensions/test/xpcshell/test_ext_settings_overrides_search.js
@@ -10,6 +10,7 @@ const { setTimeout } = ChromeUtils.import("resource://gre/modules/Timer.jsm");
 
 let delay = () => new Promise(resolve => setTimeout(resolve, 0));
 
+const kSearchFormURL = "https://example.com/searchform";
 const kSearchEngineURL = "https://example.com/?search={searchTerms}";
 const kSearchSuggestURL = "https://example.com/?suggest={searchTerms}";
 const kSearchTerm = "foo";
@@ -43,6 +44,7 @@ add_task(async function test_extension_adding_engine() {
         search_provider: {
           name: "MozSearch",
           keyword: "MozSearch",
+          search_form: kSearchFormURL,
           search_url: kSearchEngineURL,
           suggest_url: kSearchSuggestURL,
         },
@@ -89,6 +91,7 @@ add_task(async function test_extension_adding_engine() {
     "Suggest URLs should match"
   );
 
+  equal(engine.searchForm, kSearchFormURL, "Search form URLs should match");
   await ext1.unload();
   await delay();
 
diff --git a/toolkit/components/search/tests/xpcshell/data/engine-rel-searchform-post.xml b/toolkit/components/search/tests/xpcshell/data/engine-rel-searchform-post.xml
deleted file mode 100644
index 8b6eb7cab03b..000000000000
--- a/toolkit/components/search/tests/xpcshell/data/engine-rel-searchform-post.xml
+++ /dev/null
@@ -1,6 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<SearchPlugin xmlns="http://www.mozilla.org/2006/browser/search/">
-<ShortName>engine-rel-searchform-post.xml</ShortName>
-<Url type="text/html" method="POST" template="http://engine-rel-searchform-post.xml/POST" rel="searchform"/>
-<SearchForm>http://engine-rel-searchform-post.xml/?search</SearchForm>
-</SearchPlugin>
diff --git a/toolkit/components/search/tests/xpcshell/data/engine-rel-searchform-post/manifest.json b/toolkit/components/search/tests/xpcshell/data/engine-rel-searchform-post/manifest.json
deleted file mode 100644
index bb53d66909e9..000000000000
--- a/toolkit/components/search/tests/xpcshell/data/engine-rel-searchform-post/manifest.json
+++ /dev/null
@@ -1,17 +0,0 @@
-{
-  "name": "engine-rel-searchform-post.xml",
-  "manifest_version": 2,
-  "version": "1.0",
-  "applications": {
-    "gecko": {
-      "id": "engine-rel-searchform-post@search.mozilla.org"
-    }
-  },
-  "hidden": true,
-  "chrome_settings_overrides": {
-    "search_provider": {
-      "name": "engine-rel-searchform-post.xml",
-      "search_url": "https://engine-rel-searchform-post.xml/POST"
-    }
-  }
-}
diff --git a/toolkit/components/search/tests/xpcshell/data/engine-rel-searchform.xml b/toolkit/components/search/tests/xpcshell/data/engine-rel-searchform.xml
deleted file mode 100644
index bcd164877ae8..000000000000
--- a/toolkit/components/search/tests/xpcshell/data/engine-rel-searchform.xml
+++ /dev/null
@@ -1,5 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<SearchPlugin xmlns="http://www.mozilla.org/2006/browser/search/">
-<ShortName>engine-rel-searchform.xml</ShortName>
-<Url type="text/html" method="GET" template="http://engine-rel-searchform.xml/?search" rel="searchform"/>
-</SearchPlugin>
diff --git a/toolkit/components/search/tests/xpcshell/data/engine-rel-searchform/manifest.json b/toolkit/components/search/tests/xpcshell/data/engine-rel-searchform/manifest.json
deleted file mode 100644
index ebed283aac0b..000000000000
--- a/toolkit/components/search/tests/xpcshell/data/engine-rel-searchform/manifest.json
+++ /dev/null
@@ -1,17 +0,0 @@
-{
-  "name": "engine-rel-searchform.xml",
-  "manifest_version": 2,
-  "version": "1.0",
-  "applications": {
-    "gecko": {
-      "id": "engine-rel-searchform@search.mozilla.org"
-    }
-  },
-  "hidden": true,
-  "chrome_settings_overrides": {
-    "search_provider": {
-      "name": "engine-rel-searchform.xml",
-      "search_url": "https://engine-rel-searchform.xml/?search"
-    }
-  }
-}
diff --git a/toolkit/components/search/tests/xpcshell/opensearch/post.xml b/toolkit/components/search/tests/xpcshell/opensearch/post.xml
index 3b1cfd236be3..621e49c872a0 100644
--- a/toolkit/components/search/tests/xpcshell/opensearch/post.xml
+++ b/toolkit/components/search/tests/xpcshell/opensearch/post.xml
@@ -3,4 +3,6 @@
   <Url type="text/html" method="POST" template="https://example.com/post">
     <Param name="searchterms" value="{searchTerms}"/>
   </Url>
+  <Url type="text/html" method="POST" template="http://engine-rel-searchform-post.xml/POST" rel="searchform"/>
+  <SearchForm>http://engine-rel-searchform-post.xml/?search</SearchForm>
 </OpenSearchDescription>
diff --git a/toolkit/components/search/tests/xpcshell/opensearch/suggestion.xml b/toolkit/components/search/tests/xpcshell/opensearch/suggestion.xml
index 539b8589892e..846265e06802 100644
--- a/toolkit/components/search/tests/xpcshell/opensearch/suggestion.xml
+++ b/toolkit/components/search/tests/xpcshell/opensearch/suggestion.xml
@@ -11,6 +11,5 @@
      template="https://example.com/suggest">
   <Param name="suggestion" value="{searchTerms}"/>
 </Url>
-
-<SearchForm>https://example.com/</SearchForm>
+<Url type="text/html" method="GET" template="http://engine-rel-searchform.xml/?search" rel="searchform"/>
 </OpenSearchDescription>
diff --git a/toolkit/components/search/tests/xpcshell/test_opensearch.js b/toolkit/components/search/tests/xpcshell/test_opensearch.js
index 47b4749b6a52..d493bb58eb3e 100644
--- a/toolkit/components/search/tests/xpcshell/test_opensearch.js
+++ b/toolkit/components/search/tests/xpcshell/test_opensearch.js
@@ -17,12 +17,16 @@ const tests = [
     file: "simple.xml",
     name: "simple",
     description: "A small test engine",
+    searchForm: "https://example.com/",
     searchUrl: "https://example.com/search?q=foo",
   },
   {
     file: "post.xml",
     name: "Post",
     description: "",
+    // The POST method is not supported for `rel="searchform"` so we fallback
+    // to the `SearchForm` url.
+    searchForm: "http://engine-rel-searchform-post.xml/?search",
     searchUrl: "https://example.com/post",
     searchPostData: "searchterms=foo",
   },
@@ -30,6 +34,7 @@ const tests = [
     file: "suggestion.xml",
     name: "suggestion",
     description: "A small engine with suggestions",
+    searchForm: "http://engine-rel-searchform.xml/?search",
     searchUrl: "https://example.com/search?q=foo",
     suggestUrl: "https://example.com/suggest?suggestion=foo",
   },
@@ -37,6 +42,7 @@ const tests = [
     file: "suggestion-alternate.xml",
     name: "suggestion-alternate",
     description: "A small engine with suggestions",
+    searchForm: "https://example.com/",
     searchUrl: "https://example.com/search?q=foo",
     suggestUrl: "https://example.com/suggest?suggestion=foo",
   },
@@ -44,6 +50,7 @@ const tests = [
     file: "mozilla-ns.xml",
     name: "mozilla-ns",
     description: "An engine using mozilla namespace",
+    searchForm: "https://example.com/",
     // mozilla-ns.xml also specifies a MozParam. However, they are only
     // valid for app-provided engines, and hence the param should not show
     // here.
@@ -104,6 +111,12 @@ for (const test of tests) {
       );
     }
 
+    Assert.equal(
+      engine.searchForm,
+      test.searchForm,
+      "Should have the correct search form url"
+    );
+
     submission = engine.getSubmission("foo", SearchUtils.URL_TYPE.SUGGEST_JSON);
     if (test.suggestUrl) {
       Assert.equal(
diff --git a/toolkit/components/search/tests/xpcshell/test_rel_searchform.js b/toolkit/components/search/tests/xpcshell/test_rel_searchform.js
deleted file mode 100644
index 45f1191f1869..000000000000
--- a/toolkit/components/search/tests/xpcshell/test_rel_searchform.js
+++ /dev/null
@@ -1,30 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
- *    http://creativecommons.org/publicdomain/zero/1.0/ */
-
-/*
- * Tests that <Url rel="searchform"/> is properly recognized as a searchForm.
- */
-
-"use strict";
-
-add_task(async function setup() {
-  useHttpServer();
-  await AddonTestUtils.promiseStartupManager();
-});
-
-add_task(async function test_rel_searchform() {
-  let engineNames = [
-    "engine-rel-searchform.xml",
-    "engine-rel-searchform-post.xml",
-  ];
-
-  // The final searchForm of the engine should be a URL whose domain is the
-  // <ShortName> in the engine's XML and that has a ?search parameter.  The
-  // point of the ?search parameter is to avoid accidentally matching the value
-  // returned as a last resort by Engine's searchForm getter, which is simply
-  // the prePath of the engine's first HTML <Url>.
-  let items = engineNames.map(e => ({ name: e, xmlFileName: e }));
-  for (let engine of await addTestEngines(items)) {
-    Assert.equal(engine.searchForm, "http://" + engine.name + "/?search");
-  }
-});
diff --git a/toolkit/components/search/tests/xpcshell/xpcshell-common.ini b/toolkit/components/search/tests/xpcshell/xpcshell-common.ini
index cc9f22118aa9..613f52c4d4e2 100644
--- a/toolkit/components/search/tests/xpcshell/xpcshell-common.ini
+++ b/toolkit/components/search/tests/xpcshell/xpcshell-common.ini
@@ -60,7 +60,6 @@ support-files =
 [test_parseSubmissionURL.js]
 [test_pref.js]
 [test_purpose.js]
-[test_rel_searchform.js]
 [test_require_engines_in_cache.js]
 [test_remove_profile_engine.js]
 [test_resultDomain.js]
diff --git a/toolkit/components/search/tests/xpcshell/xpcshell-legacyconfig.ini b/toolkit/components/search/tests/xpcshell/xpcshell-legacyconfig.ini
index b8121beeb04a..6431f63091db 100644
--- a/toolkit/components/search/tests/xpcshell/xpcshell-legacyconfig.ini
+++ b/toolkit/components/search/tests/xpcshell/xpcshell-legacyconfig.ini
@@ -21,10 +21,6 @@ support-files =
   data/engine-reordered/manifest.json
   data/engineMaker.sjs
   data/engine-pref/manifest.json
-  data/engine-rel-searchform/manifest.json
-  data/engine-rel-searchform.xml
-  data/engine-rel-searchform-post/manifest.json
-  data/engine-rel-searchform-post.xml
   data/engine-rel-searchform-purpose/manifest.json
   data/engine-system-purpose/manifest.json
   data/engineImages.xml
diff --git a/toolkit/components/search/tests/xpcshell/xpcshell.ini b/toolkit/components/search/tests/xpcshell/xpcshell.ini
index e421599bb370..95d0fb49d187 100644
--- a/toolkit/components/search/tests/xpcshell/xpcshell.ini
+++ b/toolkit/components/search/tests/xpcshell/xpcshell.ini
@@ -21,10 +21,6 @@ support-files =
   data/engine-reordered/manifest.json
   data/engineMaker.sjs
   data/engine-pref/manifest.json
-  data/engine-rel-searchform/manifest.json
-  data/engine-rel-searchform.xml
-  data/engine-rel-searchform-post/manifest.json
-  data/engine-rel-searchform-post.xml
   data/engine-rel-searchform-purpose/manifest.json
   data/engine-system-purpose/manifest.json
   data/engineImages.xml