Test suite: Only run the c1,c2 hostname test in CI

test/script.jl

@@ -3,27 +3,77 @@
 # We don't use `using Foo` here.
 # We either use `using Foo: hello, world`, or we use `import Foo`.
 # https://github.com/JuliaLang/julia/pull/42080
-using Distributed: addprocs, workers, nworkers, remotecall_fetch
+using Distributed: addprocs, workers, nworkers, remotecall_fetch, @everywhere
 using SlurmClusterManager: SlurmManager
+using Test: @testset, @test
 
 addprocs(SlurmManager())
 
-# We intentionally do not use `@assert` here.
-# In a future minor release of Julia, `@assert`s may be disabled by default.
-const SLURM_NTASKS = parse(Int, ENV["SLURM_NTASKS"])
-if nworkers() != SLURM_NTASKS
-  msg = "Test failed: nworkers=$(nworkers()) does not match SLURM_NTASKS=$(SLURM_NTASKS)"
-  error(msg)
+# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+
+# Instructions:
+# To run tests outside of CI, set e.g.
+# `export JULIA_SLURMCLUSTERMANAGER_IS_CI=false`
+# in your Bash session before you launch the Slurm job.
+function is_ci()
+  name = "JULIA_SLURMCLUSTERMANAGER_IS_CI"
+
+  # We intentionally default to true.
+  # This allows things to work in our CI (which is inside of Docker).
+  default_value = "true"
+
+  value_str = strip(get(ENV, name, default_value))
+  value_b = parse(Bool, value_str)
+  return value_b
+end
+
+function get_SLURM_NTASKS()
+  return parse(Int, ENV["SLURM_NTASKS"])
 end
 
-const hosts = map(workers()) do id
-  remotecall_fetch(() -> gethostname(), id)
+function get_observed_hosts()
+  observed_hosts = map(workers()) do id
+    remotecall_fetch(() -> gethostname(), id)
+  end
+  sort!(observed_hosts)
+  return observed_hosts
 end
-sort!(hosts)
-println("List of hosts: ", hosts)
 
-# We don't use `@assert` here, for reason described above.
-if hosts != ["c1", "c1", "c2", "c2"]
-  msg = "Test failed: observed_hosts=$(hosts) does not match expected_hosts=[c1, c1, c2, c2]"
-  error(msg)
+# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+
+# We intentionally do not use `@assert` here.
+# In a future minor release of Julia, `@assert`s may be disabled by default.
+#
+# So instead we use `@test`.
+@testset "SlurmClusterManager/script.jl" begin
+  @show Distributed.nworkers()
+  @show get_SLURM_NTASKS()
+  @show get_observed_hosts()
+
+  @testset "Number of workers" begin
+    @test Distributed.nworkers() == get_SLURM_NTASKS()
+    @test length(Distributed.workers()) == get_SLURM_NTASKS()
+    @test length(get_observed_hosts()) == get_SLURM_NTASKS()
+  end
+
+  @testset "Hostnames of workers" begin
+    if is_ci()
+      @info "This is CI, so we will perform the hostname test"
+      @test get_observed_hosts() == ["c1", "c1", "c2", "c2"]
+    else
+      # The specific hostnames of c1 and c2 are specific to the CI setup.
+      # We don't expect people to have the same hostnames if they run the test suite locally.
+      @warn "This is not CI, so we will skip the hostname test"
+      @test_skip false
+    end
+  end
+
+  @everywhere import Distributed
+
+  # Workers report in:
+  @everywhere println("Host $(Distributed.myid()): $(gethostname())")
 end