refactor: restrict container detection by pid only when required file…

… exists

functions/_pure_detect_container_by_pid_method.fish

@@ -1,11 +1,14 @@
 function _pure_detect_container_by_pid_method \
-    --description "Linux method to detect container using /proc. see https://stackoverflow.com/a/37015387/802365"
+    --description "Linux method to detect container using /proc. see https://stackoverflow.com/a/37015387/802365" \
+    --argument-names proc_sched
 
     set --query proc_sched[1]; or set proc_sched /proc/1/sched
 
-    head -n 1 $proc_sched \
-        | string match \
-        --quiet \
-        --invert \
-        --regex 'init|systemd'
+    if test -e $proc_sched
+        head -n 1 $proc_sched \
+            | string match \
+            --quiet \
+            --invert \
+            --regex 'init|systemd'
+    end
 end

tests/_pure_detect_container_by_pid_method.test.fish

@@ -10,35 +10,67 @@ end
 setup
 
 function teardown
-    functions --erase  uname
+    functions --erase uname
 end
 
-if test (uname -s) = "Linux"
-@test "_pure_detect_container_by_pid_method: true for init" (
-    set --local proc_sched /proc/1/sched
-    echo "init (1, #threads: 1)" >$proc_sched
+set proc_sched /tmp/1/sched
+function before_each
+    functions --erase head
+end
 
-    _pure_detect_container_by_pid_method $proc_sched
-) $status -eq $SUCCESS
+function _create_proc_sched_file --argument-names proc_sched
+    mkdir -p (dirname $proc_sched)
+    touch $proc_sched
 end
 
-if test (uname -s) = "Linux"
-@test "_pure_detect_container_by_pid_method: true for systemd" (
-    set --local proc_sched /proc/1/sched
-    echo "systemd (1, #threads: 1)" >$proc_sched
+before_each
+@test "_pure_detect_container_by_pid_method: ignored when /proc/*/scheg is missing" (
+    rm -rf $proc_sched
+    function head; echo (status function) > /tmp/called; end # spy
 
     _pure_detect_container_by_pid_method $proc_sched
-) $status -eq $SUCCESS
-end
+    _has_called head
+) $status -eq $FAILURE
+
 
-if test (uname -s) = "Linux"
-@test "_pure_detect_container_by_pid_method: true for Github Action" (
-    set --local proc_sched /proc/1/sched
-    echo "systemd (1, #threads: 1)" >$proc_sched
+before_each
+@test "_pure_detect_container_by_pid_method: when /proc/*/scheg exists" (
+    _create_proc_sched_file $proc_sched
+    function head; echo (status function) > /tmp/called; end # spy
 
     _pure_detect_container_by_pid_method $proc_sched
+    _has_called head
 ) $status -eq $SUCCESS
+
+
+if test (uname -s) = Linux
+    _create_proc_sched_file $proc_sched
+    before_each
+    @test "_pure_detect_container_by_pid_method: false when detecting init in /proc/1/sched" (
+        echo "init (1, #threads: 1)" >$proc_sched
+
+        _pure_detect_container_by_pid_method $proc_sched
+    ) $status -eq $FAILURE
 end
 
+if test (uname -s) = Linux
+    before_each
+    @test "_pure_detect_container_by_pid_method: false when detecting systemd in /proc/1/sched" (
+        _create_proc_sched_file $proc_sched
+        echo "systemd (1, #threads: 1)" >$proc_sched
+
+        _pure_detect_container_by_pid_method $proc_sched
+    ) $status -eq $FAILURE
+end
+
+if test (uname -s) = Linux
+    before_each
+    @test "_pure_detect_container_by_pid_method: true when 1st process is neither systemd nor init in /proc/1/sched" (
+        _create_proc_sched_file $proc_sched
+        echo "fish (1, #threads: 1)" >$proc_sched
+
+        _pure_detect_container_by_pid_method $proc_sched
+    ) $status -eq $SUCCESS
+end
 
-teardown
+# teardown

tests/fixtures/constants.fish

@@ -27,3 +27,14 @@ end
 function _print_filename --argument-names filename
     echo (set_color cyan)$filename(set_color normal)
 end
+
+function _has_called \
+    --description "check spy method XYZ write to the /tmp/called file when called" \
+    --argument-names spy # name of the method
+
+    if test -r /tmp/called
+        grep -c -q $spy /tmp/called # check spy was called
+    else
+        return $FAILURE
+    end
+end