modify tests

Author: Harris-Miller

test/modify.test.ts

@@ -0,0 +1,34 @@
+import { expectError, expectType } from 'tsd';
+
+import { modify, toUpper, add, identity, pipe, map } from '../es';
+
+type Obj = {
+  foo: string;
+  bar: number;
+};
+
+expectType<Obj>(modify('foo', toUpper, {} as Obj));
+expectType<Obj>(modify('bar', add(1), {} as Obj));
+expectType<Obj>(modify('foo', toUpper)({} as Obj));
+expectType<Obj>(modify('bar', add(1))({} as Obj));
+expectType<Obj>(modify('foo')(toUpper)({} as Obj));
+expectType<Obj>(modify('bar')(add(1))({} as Obj));
+expectType<Obj>(modify('foo')(toUpper, {} as Obj));
+expectType<Obj>(modify('bar')(add(1), {} as Obj));
+
+// fails when function has wrong argument type
+expectError(modify('foo', add(1), {} as Obj));
+expectError(modify('bar', toUpper, {} as Obj));
+
+// fails when key does not exist on Obj
+expectError(modify('unknownKey', toUpper, {} as Obj));
+
+// works with generic fn
+expectType<Obj>(modify('foo', identity, {} as Obj));
+
+// pipe and map sanity checks
+const f = pipe(
+  map<Obj, Obj>(modify('foo', toUpper))
+);
+
+expectType<Obj[]>(f([] as Obj[]));