Test suite: Change @asserts to errors, and change bare using Foo …

…to `using Foo: name, anothername, ...`

test/script.jl

@@ -1,13 +1,28 @@
 #!/usr/bin/env julia
 
-using Distributed, SlurmClusterManager
+# 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 SlurmClusterManager: SlurmManager
+
 addprocs(SlurmManager())
 
-@assert nworkers() == parse(Int, ENV["SLURM_NTASKS"])
+# 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)
+end
 
-hosts = map(workers()) do id
+const hosts = map(workers()) do id
   remotecall_fetch(() -> gethostname(), id)
 end
 sort!(hosts)
 
-@assert hosts == ["c1", "c1", "c2", "c2"]
+# 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