fix: treat form-data bodies as binary (#20144)

packages/net-stubbing/lib/server/util.ts

@@ -251,6 +251,10 @@ export function getBodyEncoding (req: CyHttpMessages.IncomingRequest): BodyEncod
     if (contentType.includes('charset=utf-8') || contentType.includes('charset="utf-8"')) {
       return 'utf8'
     }
+
+    if (contentType.includes('multipart/form-data')) {
+      return 'binary'
+    }
   }
 
   // with fallback to inspecting the buffer using

packages/net-stubbing/test/unit/util-spec.ts

@@ -69,5 +69,19 @@ describe('net-stubbing util', () => {
 
       expect(getBodyEncoding(req), 'image').to.equal('binary')
     })
+
+    it('returns binary for form-data bodies', () => {
+      const formDataRequest = {
+        body: Buffer.from('hello world'),
+        headers: {
+          'content-type': 'multipart/form-data',
+        },
+        method: 'POST',
+        url: 'somewhere',
+        httpVersion: '1.1',
+      }
+
+      expect(getBodyEncoding(formDataRequest)).to.equal('binary')
+    })
   })
 })