[FIX] mail: adds a test for the chatter of new records

This commit adds a test for the fix odoo/odoo/pull/58769 that
ensures that the chatter is properly cleared when creating a new record.

task-2348472

closes odoo/odoo#60731

X-original-commit: 5e46850072f142fb17b72d8738dc4f1c60e3a786
Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

addons/mail/static/src/widgets/form_renderer/form_renderer_tests.js

@@ -922,6 +922,40 @@ QUnit.test('Attachments that have been unlinked from server should be visually u
     );
 });
 
+QUnit.test('chatter just contains "creating a new record" message during the creation of a new record after having displayed a chatter for an existing record', async function (assert) {
+    assert.expect(2);
+
+    this.data['res.partner'].records.push({ id: 12 });
+    await this.createView({
+        data: this.data,
+        hasView: true,
+        View: FormView,
+        model: 'res.partner',
+        res_id: 12,
+        arch: `
+            <form>
+                <div class="oe_chatter">
+                    <field name="message_ids"/>
+                </div>
+            </form>
+        `,
+    });
+
+    await afterNextRender(() => {
+        document.querySelector('.o_form_button_create').click();
+    });
+    assert.containsOnce(
+        document.body,
+        '.o_Message',
+        "Should have a single message when creating a new record"
+    );
+    assert.strictEqual(
+        document.querySelector('.o_Message_content').textContent,
+        'Creating a new record...',
+        "the message content should be in accord to the creation of this record"
+    );
+});
+
 });
 });
 });