Improve retry_until (#1725)

* Fix bug in epoch millisecond calculation
* Include timeout milliseconds in exception message
* Support assertions in retry_until

Previously, retry_until would only work with boolean conditions.

This change supports assertions in code being retried, which requires
fewer changes to wrap existing code containing assertions.

2 files changed, 42 insertions, 8 deletions

diff --git a/test/elixir/test/helper_test.exs b/test/elixir/test/helper_test.exs
new file mode 100644
index 000000000..e2070c457
--- /dev/null
+++ b/test/elixir/test/helper_test.exs
@@ -0,0 +1,28 @@
+defmodule HelperTest do
+  use CouchTestCase
+
+  @moduledoc """
+  Test helper code
+  """
+
+  test "retry_until handles boolean conditions", _context do
+    retry_until fn ->
+      true
+    end
+  end
+
+  test "retry_until handles assertions", _context do
+    retry_until fn ->
+      assert true
+    end
+  end
+
+  test "retry_until times out", _context do
+    assert_raise RuntimeError, ~r/^timed out after \d+ ms$/, fn ->
+      retry_until fn ->
+        assert false
+      end, 1, 5
+    end
+  end
+
+end
diff --git a/test/elixir/test/test_helper.exs b/test/elixir/test/test_helper.exs
index e8f394345..7e685c837 100644
--- a/test/elixir/test/test_helper.exs
+++ b/test/elixir/test/test_helper.exs
@@ -200,20 +200,26 @@ defmodule CouchTestCase do
       end
 
       defp retry_until(condition, start, sleep, timeout) do
-        if (now(:ms) > start + timeout) do
-          raise "timed out"
+        now = now(:ms)
+        if now > start + timeout do
+          raise "timed out after #{now - start} ms"
         else
-          if condition.() do
-            :ok
-          else
-            :timer.sleep(sleep)
-            retry_until(condition, start, sleep, timeout)
+          try do
+            if condition.() do
+              :ok
+            else
+              raise ExUnit.AssertionError
+            end
+          rescue
+            ExUnit.AssertionError ->
+              :timer.sleep(sleep)
+              retry_until(condition, start, sleep, timeout)
           end
         end
       end
 
       defp now(:ms) do
-        div(:erlang.system_time, 100000)
+        div(:erlang.system_time, 1000000)
       end
 
       @spec rev(map(), map()) :: map()