backport v2 PRs

Author: t-bltg

PlotThemes/test/Project.toml

@@ -1,2 +1,3 @@
 [deps]
+PlotUtils = "995b91a9-d308-5afd-9ec6-746e21dbc043"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"

PlotThemes/test/runtests.jl

@@ -1,4 +1,15 @@
 using PlotThemes
 using Test, PlotUtils
 
-@test in(:sand, keys(PlotThemes._themes))
+@testset "basics" begin
+    @test :sand ∈ keys(PlotThemes._themes)
+
+    palette = theme_palette(:wong)
+    @test palette isa ColorPalette
+
+    thm = PlotTheme(PlotThemes._dark; palette)
+    @test thm isa PlotTheme
+
+    add_theme(:custom, thm)
+    @test theme_palette(:custom) == palette
+end