Add Trixi as test dependency

test/Project.toml

@@ -1,2 +1,6 @@
 [deps]
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+Trixi = "a7f1ee26-1774-49b1-8366-f1abc58fbfcb"
+
+[compat]
+Trixi = "0.5"

test/runtests.jl

@@ -1,7 +1,22 @@
 using TrixiShallowWater
 using Test
 
-@testset "TrixiShallowWater.jl" begin
-  @test TrixiShallowWater.foo() == true
-  @test TrixiShallowWater.bar() == false
+# We run tests in parallel with CI jobs setting the `TRIXI_TEST` environment
+# variable to determine the subset of tests to execute.
+# By default, we just run the threaded tests since they are relatively cheap
+# and test a good amount of different functionality.
+const TRIXI_TEST = get(ENV, "TRIXI_TEST", "all")
+const TRIXI_MPI_NPROCS = clamp(Sys.CPU_THREADS, 2, 3)
+const TRIXI_NTHREADS = clamp(Sys.CPU_THREADS, 2, 3)
+
+@time @testset "TrixiShallowWater.jl tests" begin
+    @time if TRIXI_TEST == "all" || TRIXI_TEST == "mpi"
+        @test TrixiShallowWater.foo() == true
+        @test TrixiShallowWater.bar() == false
+    end
+
+    @time if TRIXI_TEST == "all" || TRIXI_TEST == "upstream"
+        @test TrixiShallowWater.foo() == true
+        @test TrixiShallowWater.bar() == false
+    end
 end