Add tests for contour levels and the start of Plotly tests

- Test that the `levels` keyword argument is correctly stored.
- For the Plotly (and PlotlyJS) backend, test that `levels`
  is correctly converted to backend-specific settings.

test/runtests.jl

@@ -31,6 +31,7 @@ end # testset
 include("test_defaults.jl")
 include("test_pipeline.jl")
 include("test_axes.jl")
+include("test_contours.jl")
 include("test_axis_letter.jl")
 include("test_components.jl")
 include("test_shorthands.jl")
@@ -38,6 +39,7 @@ include("integration_dates.jl")
 include("test_recipes.jl")
 include("test_hdf5plots.jl")
 include("test_pgfplotsx.jl")
+include("test_plotly.jl")
 
 reference_dir(args...) =
     joinpath(homedir(), ".julia", "dev", "PlotReferenceImages", args...)

test/test_contours.jl

@@ -0,0 +1,31 @@
+using Plots, Test
+
+@testset "Contours" begin
+    x = (-2π):0.1:(2π)
+    y = (-π):0.1:π
+    z = cos.(y) .* sin.(x')
+
+    @testset "Default number" begin
+        @test contour(x, y, z)[1][1].plotattributes[:levels] ==
+              Plots._series_defaults[:levels]
+    end
+
+    @testset "Number" begin
+        @testset "$n contours" for n in (2, 5, 100)
+            p = contour(x, y, z, levels = n)
+            attr = p[1][1].plotattributes
+            @test attr[:seriestype] == :contour
+            @test attr[:levels] == n
+        end
+    end
+
+    @testset "Range" begin
+        levels = -1:0.5:1
+        @test contour(x, y, z, levels = levels)[1][1].plotattributes[:levels] == levels
+    end
+
+    @testset "Set of levels" begin
+        levels = [-1, 0.25, 0, 0.25, 1]
+        @test contour(x, y, z, levels = levels)[1][1].plotattributes[:levels] == levels
+    end
+end

test/test_plotly.jl

@@ -0,0 +1,57 @@
+using Plots, Test
+
+@testset "Plotly" begin
+    @testset "Basic" begin
+        @test plotly() == Plots.PlotlyBackend()
+        @test backend() == Plots.PlotlyBackend()
+
+        p = plot(rand(10))
+        @test isa(p, Plots.Plot) == true
+    end
+
+    @testset "Contours" begin
+        x = (-2π):0.1:(2π)
+        y = (-π):0.1:π
+        z = cos.(y) .* sin.(x')
+
+        @testset "Contour numbers" begin
+            @testset "Default" begin
+                @test Plots.plotly_series(contour(x, y, z))[1][:ncontours] ==
+                      Plots._series_defaults[:levels] + 2
+            end
+            @testset "Specified number" begin
+                @test Plots.plotly_series(contour(x, y, z, levels = 10))[1][:ncontours] ==
+                      12
+            end
+        end
+
+        @testset "Contour values" begin
+            @testset "Range" begin
+                levels = -1:0.5:1
+                p = contour(x, y, z, levels = levels)
+                @test p[1][1].plotattributes[:levels] == levels
+                @test Plots.plotly_series(p)[1][:contours][:start] == first(levels)
+                @test Plots.plotly_series(p)[1][:contours][:end] == last(levels)
+                @test Plots.plotly_series(p)[1][:contours][:size] == step(levels)
+            end
+
+            @testset "Set of contours" begin
+                levels = [-1, -0.25, 0, 0.25, 1]
+                levels_range =
+                    range(first(levels), stop = last(levels), length = length(levels))
+                p = contour(x, y, z, levels = levels)
+                @test p[1][1].plotattributes[:levels] == levels
+                series_dict = @test_logs (
+                    :warn,
+                    "setting arbitrary contour levels with Plotly backend " *
+                    "is not supported; use a range to set equally-spaced contours or an " *
+                    "integer to set the approximate number of contours with the keyword " *
+                    "`levels`. Using levels -1.0:0.5:1.0",
+                ) Plots.plotly_series(p)
+                @test series_dict[1][:contours][:start] == first(levels_range)
+                @test series_dict[1][:contours][:end] == last(levels_range)
+                @test series_dict[1][:contours][:size] == step(levels_range)
+            end
+        end
+    end
+end