add tests

test/new.jl

@@ -2164,6 +2164,41 @@ end
     end
 end
 
+#
+# # compat
+#
+@testset "Pkg.compat" begin
+    # State changes
+    isolate(loaded_depot=true) do
+        Pkg.add("Example")
+        iob = IOBuffer()
+        Pkg.compat(io = iob)
+        output = String(take!(iob))
+        @test occursin(r"Compat `.+Project.toml`", output)
+        @test occursin(r"\[7876af07\] *Example *none", output)
+        @test occursin(r"julia *none", output)
+
+        Pkg.compat!("Example", "0.2,0.3")
+        @test Pkg.compat("Example") == "0.2,0.3"
+        Pkg.compat(io = iob)
+        output = String(take!(iob))
+        @test occursin(r"Compat `.+Project.toml`", output)
+        @test occursin(r"\[7876af07\] *Example *0.2,0.3", output)
+        @test occursin(r"julia *none", output)
+
+        Pkg.compat!("Example", nothing)
+        Pkg.compat!("julia", "1.8")
+        @test Pkg.compat("Example") == nothing
+        @test Pkg.compat("julia") == "1.8"
+        Pkg.compat(io = iob)
+        output = String(take!(iob))
+        @test occursin(r"Compat `.+Project.toml`", output)
+        @test occursin(r"\[7876af07\] *Example *none", output)
+        @test occursin(r"julia *1.8", output)
+    end
+end
+
+
 #
 # # Caching
 #

test/repl.jl

@@ -645,6 +645,15 @@ end
     end
 end
 
+@testset "compat" begin
+    temp_pkg_dir() do project_path
+        pkg"""
+        add Example Random
+        compat
+        """
+    end
+end
+
 @testset "subcommands" begin
     temp_pkg_dir() do project_path; cd_tempdir() do tmpdir; with_temp_env() do
         Pkg.REPLMode.pkg"package add Example"