add ElasticManager test

README.md

@@ -145,7 +145,7 @@ ElasticManager(addr, port) = ElasticManager(;addr=addr, port=port)
 ElasticManager(addr, port, cookie) = ElasticManager(;addr=addr, port=port, cookie=cookie)
 ```
 
-On Linux, you can set `addr=:auto` to automatically use the host's private IP address on the local network, which will allow other workers on this network to connect. You can also use `port=0` to let the OS choose a random free port for you (some systems may not support this). Once created, printing the `ElasticManager` object prints the command which you can run on workers to connect them to the master, e.g.:
+On Linux and Mac, you can set `addr=:auto` to automatically use the host's private IP address on the local network, which will allow other workers on this network to connect. You can also use `port=0` to let the OS choose a random free port for you (some systems may not support this). Once created, printing the `ElasticManager` object prints the command which you can run on workers to connect them to the master, e.g.:
 
 ```julia
 julia> em = ElasticManager(addr=:auto, port=0)

src/elastic.jl

@@ -137,9 +137,19 @@ end
 
 function get_private_ip()
     if Sys.islinux()
-        IPv4(strip(read(`hostname --ip-address`, String)))
+        cmd = `hostname --ip-address`
+    elseif Sys.isapple()
+        cmd = `ipconfig getifaddr en0`
     else
-        error("addr=:auto is only supported on Linux")
+        error("`addr=:auto` is only supported on Linux and Mac")
+    end
+    try
+        return IPv4(first(split(strip(read(cmd, String)))))
+    catch err
+        error("""Failed to automatically get host's IP address (output below). Please specify `addr=` explicitly.
+        \$ $(repr(cmd))
+        $err
+        """)
     end
 end
 

test/runtests.jl

@@ -1,2 +1,18 @@
-# only package loading for now
+using Test
 using ClusterManagers
+
+TIMEOUT = 10.
+
+@testset "ElasticManager" begin
+
+    em = ElasticManager(addr=:auto, port=0)
+
+    # launch worker
+    run(`sh -c $(ClusterManagers.get_connect_cmd(em))`, wait=false)
+
+    # wait at most TIMEOUT seconds for it to connect
+    @test :ok == timedwait(TIMEOUT) do
+        length(em.active) == 1
+    end
+
+end