diff --git a/go/testdata/format-netspoc/format-netspoc.t b/go/testdata/format-netspoc/format-netspoc.t
index 7dadb7419..82236f14d 100644
--- a/go/testdata/format-netspoc/format-netspoc.t
+++ b/go/testdata/format-netspoc/format-netspoc.t
@@ -1302,3 +1302,14 @@ xxx
 =WARNING=NONE
 
 ############################################################
+=TITLE=Can't change readonly file
+=INPUT=
+--f1
+group:g1=;
+=SETUP=
+chmod u-w netspoc/f1
+=ERROR=
+Error: Can't open f1: permission denied
+=END=
+
+############################################################
diff --git a/go/testdata/options.t b/go/testdata/options.t
index ee61acbea..3d5b72af7 100644
--- a/go/testdata/options.t
+++ b/go/testdata/options.t
@@ -160,7 +160,6 @@ Aborted
 =TITLE=Can't create out directory
 =SETUP=touch out
 =INPUT=
--- topology
 network:n1 = { ip = 10.1.1.0/24; }
 =WITH_OUTDIR=
 =ERROR=
@@ -168,6 +167,24 @@ Error: Can't mkdir out: file exists
 Aborted
 =END=
 
+############################################################
+=TITLE=Can't write to out directory
+=SETUP=
+mkdir out
+chmod u-w out
+=INPUT=
+network:n1 = { ip = 10.1.1.0/24; }
+router:r1 = {
+ managed;
+ model = ASA;
+ interface:n1 = { ip = 10.1.1.1; hardware = n1; }
+}
+=WITH_OUTDIR=
+=ERROR=
+Error: Can't open out/r1.config: permission denied
+Aborted
+=END=
+
 ############################################################
 =TITLE=Can't write code file
 =SETUP=
diff --git a/go/testdata/reuse-previous.t b/go/testdata/reuse-previous.t
index 0a6ad7ed4..9c77435f5 100644
--- a/go/testdata/reuse-previous.t
+++ b/go/testdata/reuse-previous.t
@@ -130,3 +130,17 @@ Aborted
 =END=
 
 ############################################################
+=TITLE=.prev is file
+=SETUP=
+mkdir out/
+touch out/.prev
+chmod u-w out/.prev
+chmod u-x out
+=INPUT=
+-- topology
+network:n1 = { ip = 10.1.1.0/24; }
+=WITH_OUTDIR=
+=ERROR=
+Error: Can't mkdir out/.prev: permission denied
+Aborted
+=END=