fix: improve filter typing (#1077)

Author: eddyerburgh

packages/test-utils/types/index.d.ts

@@ -113,11 +113,17 @@ export interface Wrapper<V extends Vue | null> extends BaseWrapper {
 }
 
 export interface WrapperArray<V extends Vue> extends BaseWrapper {
-  readonly length: number
-  readonly wrappers: Array<Wrapper<V>>
-
-  at (index: number): Wrapper<V>
-  filter (predicate: Function): WrapperArray<Vue>
+  readonly length: number;
+  readonly wrappers: Array<Wrapper<V>>;
+
+  at(index: number): Wrapper<V>;
+  filter(
+    predicate: (
+      value: Wrapper<V>,
+      index: number,
+      array: Wrapper<V>[]
+    ) => any
+  ): WrapperArray<Vue>;
 }
 
 interface WrapperOptions {

packages/test-utils/types/test/wrapper.ts

@@ -79,7 +79,11 @@ wrapper.attributes('foo')
  */
 let num: number = array.length
 found = array.at(1)
-array = array.filter((a: any) => a === true)
+array = array.filter((w, i, arr) => {
+  i + 2
+  arr.length
+  return w.is('div')
+})
 
 let createdWrapper = createWrapper(new Vue().$mount())
 createdWrapper.text()