support regex in body

mod.ts

@@ -133,7 +133,7 @@ export const makeFetch = (h: HandlerOrListener): FetchFunction => {
         assertEquals(
           header,
           b.join(','),
-          `expected header ${a} to match regexp ${b}, got ${header}`,
+          `expected header ${a} to match ${b.join(', ')}, got ${header}`,
         )
       } else {
         assertEquals(
@@ -152,7 +152,13 @@ export const makeFetch = (h: HandlerOrListener): FetchFunction => {
       }
     }
     const expectBody = (a: unknown) => {
-      assertEquals(data, a, `Expected to have body ${a}, got ${data}`)
+      if (a instanceof RegExp) {
+        assertMatch(
+          data as string,
+          a,
+          `Expected body to match regexp ${a}, got ${data}`,
+        )
+      } else assertEquals(data, a, `Expected to have body ${a}, got ${data}`)
     }
 
     // deno-lint-ignore no-explicit-any

mod_test.ts

@@ -184,10 +184,8 @@ describe('expectHeader', () => {
     try {
       res.expectHeader('Content-Type', /image/)
     } catch (e) {
-      expect((e as Error).message).toMatch(
-        new RegExp(
-          'Expected actual: "text/html" to match: "/image/": expected header Content-Type to match regexp /image/, got text/html',
-        ),
+      expect((e as Error).message).toEqual(
+        'Expected actual: "text/html" to match: "/image/": expected header Content-Type to match regexp /image/, got text/html',
       )
     }
   })
@@ -258,6 +256,12 @@ describe('expectBody', () => {
       expect(e).toBeDefined()
     }
   })
+  it('supports regex', async () => {
+    const handler: Handler = () => new Response('Hello World')
+    const fetch = makeFetch(handler)
+    const res = await fetch('/')
+    res.expectBody(new RegExp('Hello'))
+  })
 })
 
 describe('expect', () => {