Add test for invoke.

test/algorithm_test.cpp

@@ -61,3 +61,28 @@ TEST_CASE("scan functions correctly", "[algorithms/scan.h]") {
     REQUIRE (all_correct);
     REQUIRE (all_correct);
   });
   });
 }
 }
+
+long fib(long n) {
+  if (n <= 2) {
+    return 1;
+  }
+
+  long a, b;
+
+  pls::invoke(
+      [&a, n]() { a = fib(n - 1); },
+      [&b, n]() { b = fib(n - 2); }
+  );
+
+  return a + b;
+}
+
+TEST_CASE("invoke functions correctly", "[algorithms/invoke.h]") {
+  constexpr long fib_40 = 102334155;
+
+  malloc_scheduler_memory my_scheduler_memory{8, 2 << 12};
+  scheduler my_scheduler{&my_scheduler_memory, 2};
+  my_scheduler.perform_work([=]() {
+    REQUIRE(fib(40) == fib_40);
+  });
+}