Add tests for DateScale and DateTimeScale start/step options

Author: nkyllonen

lib/plox/date_time_scale.ex

@@ -71,7 +71,7 @@ defmodule Plox.DateTimeScale do
 
     ## Options
 
-      * `:step` - The step interval. Can be an integer number of seconds,
+      * `:step` - The step interval. Can be a non-zero integer number of seconds,
         or a tuple of `{integer, :second | :minute | :hour | :day}`.
         Defaults to `{60, :second}`.
 
@@ -93,14 +93,14 @@ defmodule Plox.DateTimeScale do
     def values(%{first: %date_time_module{}} = scale, opts) do
       step_seconds =
         case Map.get(opts, :step, {60, :second}) do
-          seconds when is_integer(seconds) -> seconds
+          seconds when is_integer(seconds) and seconds > 0 -> seconds
           {seconds, :second} -> seconds
           {minutes, :minute} -> minutes * 60
           {hours, :hour} -> hours * 3600
           {days, :day} -> days * 86_400
           _ ->
             raise ArgumentError,
-              message: "DateTimeScale: step must be an integer or a {integer, :second | :minute | :hour | :day} tuple"
+              message: "DateTimeScale: step must be a non-zero integer or a {integer, :second | :minute | :hour | :day} tuple"
         end
 
       if date_time_module == DateTime and scale.first.time_zone != "Etc/UTC" and

test/plox/date_scale_test.exs

@@ -38,7 +38,7 @@ defmodule Plox.DateScaleTest do
   describe "values/2" do
     test "with default step (1d)" do
       scale = DateScale.new(Date.range(~D[2019-01-01], ~D[2019-01-03]))
-      assert %Date.Range{first: ~D[2019-01-01], last: ~D[2019-01-03], step: 1} = Scale.values(scale)
+      assert Scale.values(scale) == Date.range(~D[2019-01-01], ~D[2019-01-03], 1)
     end
 
     test "with positive custom step in days" do
@@ -58,6 +58,24 @@ defmodule Plox.DateScaleTest do
         Scale.values(scale, %{step: 0})
       end
     end
+
+    test "with default start" do
+      scale = DateScale.new(Date.range(~D[2019-01-01], ~D[2019-01-05]))
+      assert Scale.values(scale) == Date.range(~D[2019-01-01], ~D[2019-01-05])
+    end
+
+    test "with custom start" do
+      scale = DateScale.new(Date.range(~D[2019-01-01], ~D[2019-01-05]))
+      assert Scale.values(scale, %{start: ~D[2019-01-03]}) == Date.range(~D[2019-01-03], ~D[2019-01-05])
+    end
+
+    test "raises an error with start outside range" do
+      scale = DateScale.new(Date.range(~D[2019-01-01], ~D[2019-01-05]))
+
+      assert_raise ArgumentError, fn ->
+        Scale.values(scale, %{start: ~D[2018-12-31]})
+      end
+    end
   end
 
   describe "convert_to_range/3" do

test/plox/date_time_scale_test.exs

@@ -94,6 +94,49 @@ defmodule Plox.DateTimeScaleTest do
                ~N[2019-01-01 00:00:03]
              ]
     end
+
+    test "raises an error with zero step" do
+      scale = DateTimeScale.new(~N[2019-01-01 00:00:00], ~N[2019-01-01 00:02:00])
+
+      assert_raise ArgumentError, fn ->
+        Scale.values(scale, %{step: 0})
+      end
+    end
+
+    test "raises an error with invalid step" do
+      scale = DateTimeScale.new(~N[2019-01-01 00:00:00], ~N[2019-01-01 00:02:00])
+
+      assert_raise ArgumentError, fn ->
+        Scale.values(scale, %{step: {-500, :invalid}})
+      end
+    end
+
+    test "with default start" do
+      scale = DateTimeScale.new(~N[2019-01-01 00:00:00], ~N[2019-01-01 00:02:00])
+
+      assert Scale.values(scale) == [
+               ~N[2019-01-01 00:00:00],
+               ~N[2019-01-01 00:01:00],
+               ~N[2019-01-01 00:02:00]
+             ]
+    end
+
+    test "with custom start" do
+      scale = DateTimeScale.new(~N[2019-01-01 00:00:00], ~N[2019-01-01 00:02:00])
+
+      assert Scale.values(scale, %{start: ~N[2019-01-01 00:01:00]}) == [
+               ~N[2019-01-01 00:01:00],
+               ~N[2019-01-01 00:02:00]
+             ]
+    end
+
+    test "raises an error with start outside range" do
+      scale = DateTimeScale.new(~N[2019-01-01 00:00:00], ~N[2019-01-01 00:02:00])
+
+      assert_raise ArgumentError, fn ->
+        Scale.values(scale, %{start: ~N[2019-01-01 00:03:00]})
+      end
+    end
   end
 
   describe "convert_to_range/3" do