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

Author: DilumAluthge

test/script.jl

@@ -3,11 +3,34 @@
 # 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
 
 addprocs(SlurmManager())
 
+# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+
+# 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
+
+# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+# ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+
 # 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"])
@@ -22,8 +45,19 @@ 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=$(hosts) does not match expected_hosts=[c1, c1, c2, c2]"
-  error(msg)
+if is_ci()
+  @info "This is CI, so we will perform the hostname test"
+
+  # We don't use `@assert` here, for reason described above.
+  if hosts != ["c1", "c1", "c2", "c2"]
+    msg = "Test failed: observed_hosts=$(hosts) does not match expected_hosts=[c1, c1, c2, c2]"
+    error(msg)
+  end
+else
+  @warn "This is not CI, so we will skip the hostname test"
 end
+
+@everywhere import Distributed
+
+# Workers report in:
+@everywhere println("Host $(Distributed.myid()): $(gethostname())")