a few unit tests

packages/squiggle-lang/__tests__/E/A_test.res

@@ -0,0 +1,21 @@
+open Jest
+open TestHelpers
+
+describe("E.A.getByWithFn", () => {
+  makeTest("Empty list returns None", E.A.getByWithFn([], x => x + 1, x => mod(x, 2) == 0), None)
+  makeTest(
+    "Never predicate returns None",
+    E.A.getByWithFn([1, 2, 3, 4, 5, 6], x => x + 1, _ => false),
+    None,
+  )
+  makeTest(
+    "function evaluates",
+    E.A.getByWithFn([1, 1, 1, 1, 1, 1, 1, 2, 1, 1], x => 3 * x, x => x > 4),
+    Some(6),
+  )
+  makeTest(
+    "always predicate returns fn(fst(a))",
+    E.A.getByWithFn([0, 1, 2, 3, 4, 5, 6], x => 10 + x, _ => true),
+    Some(10),
+  )
+})