maxBy and minBy tests

test/maxBy.test.ts

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+import { expectError, expectType } from 'tsd';
+
+import { __, maxBy, prop } from '../es';
+
+type Obj = {
+  str: string;
+  date: Date;
+  bool: boolean;
+};
+
+// please note how literals work in this situation
+expectType<1 | 2>(maxBy(Math.abs, 1, 2));
+// using variables that are type `number` is the more general use-case here
+const a: number = 1;
+const b: number = 2;
+expectType<number>(maxBy(Math.abs, a, b));
+// so can also upcast inline to get the same result
+expectType<number>(maxBy(Math.abs, 1 as number, 2 as number));
+// now check the other Ord types
+expectType<Obj>(maxBy(prop('str'), {} as Obj, {} as Obj));
+expectType<Obj>(maxBy(prop('bool'), {} as Obj, {} as Obj));
+expectType<Obj>(maxBy(prop('date'), {} as Obj, {} as Obj));
+
+// Placeholder
+// expectType<number>(max(__, b)(a));
+expectType<number>(maxBy(__, 1 as number, 2 as number)(Math.abs));
+// curried
+// notice how literals work fine here because `T` is pulled directly from Math.abs
+// in the full function typescript will hard union them, but here it cannot
+expectType<number>(maxBy(Math.abs)(1)(2));
+
+// don't allow different types
+expectError(maxBy(Math.abs, 1, '2'));

test/minBy.test.ts

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+import { expectError, expectType } from 'tsd';
+
+import { __, minBy, prop } from '../es';
+
+type Obj = {
+  str: string;
+  date: Date;
+  bool: boolean;
+};
+
+// please note how literals work in this situation
+expectType<1 | 2>(minBy(Math.abs, 1, 2));
+// using variables that are type `number` is the more general use-case here
+const a: number = 1;
+const b: number = 2;
+expectType<number>(minBy(Math.abs, a, b));
+// so can also upcast inline to get the same result
+expectType<number>(minBy(Math.abs, 1 as number, 2 as number));
+// now check the other Ord types
+expectType<Obj>(minBy(prop('str'), {} as Obj, {} as Obj));
+expectType<Obj>(minBy(prop('bool'), {} as Obj, {} as Obj));
+expectType<Obj>(minBy(prop('date'), {} as Obj, {} as Obj));
+
+// Placeholder
+// expectType<number>(max(__, b)(a));
+expectType<number>(minBy(__, 1 as number, 2 as number)(Math.abs));
+// curried
+// notice how literals work fine here because `T` is pulled directly from Math.abs
+// in the full function typescript will hard union them, but here it cannot
+expectType<number>(minBy(Math.abs)(1)(2));
+
+// don't allow different types
+expectError(minBy(Math.abs, 1, '2'));