diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index efbcd79..aef4e42 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -9,26 +9,60 @@ on:
 
 jobs:
   Linux:
+    strategy:
+      fail-fast: false
+      matrix:
+        volume:
+          - /tmp
+          - .
+          - /
+        asroot:
+          - name: ''
+            sudo: ''
+          - name: ' as root'
+            sudo: 'sudo '
+
+    name: Linux ${{ matrix.volume }}${{ matrix.asroot.name }}
     runs-on: ubuntu-22.04
+
     steps:
       - uses: actions/checkout@v3
       - run: sudo apt-get install -y libparted-dev libudev-dev
       - run: make all extra
 
+      - if: matrix.volume == '/'
+        run: sudo chmod a+w /
+
       - run: ./f3write -V
       - run: ./f3write --help
-      - run: ./f3write -s 2 -e 4 -w 50000 /tmp
+      - run: ${{ matrix.asroot.sudo }}./f3write -s 2 -e 4 -w 50000 ${{ matrix.volume }}
 
-      - run: stat /tmp/2.h2w
-      - run: stat /tmp/3.h2w
-      - run: stat /tmp/4.h2w
+      - run: stat ${{ matrix.volume }}/2.h2w
+      - run: stat ${{ matrix.volume }}/3.h2w
+      - run: stat ${{ matrix.volume }}/4.h2w
 
       - run: ./f3read -V
       - run: ./f3read --help
-      - run: ./f3read -s 2 -e 4 -r 50000 /tmp
+      - run: ${{ matrix.asroot.sudo }}./f3read -s 2 -e 4 -r 50000 ${{ matrix.volume }}
 
   MacOS:
+    strategy:
+      fail-fast: false
+      matrix:
+        volume:
+          - /tmp
+          - .
+          # MacOS denies `sudo chmod a+w /`
+          #- /
+        asroot:
+          - name: ''
+            sudo: ''
+          - name: ' as root'
+            sudo: 'sudo '
+
+    name: MacOS ${{ matrix.volume }}${{ matrix.asroot.name }}
     runs-on: macos-12
+
     steps:
       - uses: actions/checkout@v3
       - run: brew install argp-standalone
@@ -36,18 +70,31 @@ jobs:
 
       - run: ./f3write -V
       - run: ./f3write --help
-      - run: ./f3write -s 2 -e 4 -w 50000 /tmp
+      - run: ${{ matrix.asroot.sudo }}./f3write -s 2 -e 4 -w 50000 ${{ matrix.volume }}
 
-      - run: stat /tmp/2.h2w
-      - run: stat /tmp/3.h2w
-      - run: stat /tmp/4.h2w
+      - run: stat ${{ matrix.volume }}/2.h2w
+      - run: stat ${{ matrix.volume }}/3.h2w
+      - run: stat ${{ matrix.volume }}/4.h2w
 
       - run: ./f3read -V
       - run: ./f3read --help
-      - run: ./f3read -s 2 -e 4 -r 50000 /tmp
+      - run: ${{ matrix.asroot.sudo }}./f3read -s 2 -e 4 -r 50000 ${{ matrix.volume }}
 
   Cygwin:
+    strategy:
+      fail-fast: false
+      matrix:
+        volume:
+          - cygwin: /cygdrive/c
+            windows: 'C:'
+          - cygwin: .
+            windows: .
+          - cygwin: /
+            windows: 'C:\cygwin'
+
+    name: Cygwin ${{ matrix.volume.cygwin }}
     runs-on: windows-2022
+
     steps:
       - uses: actions/checkout@v3
 
@@ -59,12 +106,12 @@ jobs:
 
       - run: '& .\f3write.exe -V'
       - run: '& .\f3write.exe --help'
-      - run: '& .\f3write.exe -s 2 -e 4 -w 50000 /cygdrive/c'
+      - run: '& .\f3write.exe -s 2 -e 4 -w 50000 ${{ matrix.volume.cygwin }}'
 
-      - run: 'Get-Item C:\2.h2w'
-      - run: 'Get-Item C:\3.h2w'
-      - run: 'Get-Item C:\4.h2w'
+      - run: 'Get-Item ${{ matrix.volume.windows }}\2.h2w'
+      - run: 'Get-Item ${{ matrix.volume.windows }}\3.h2w'
+      - run: 'Get-Item ${{ matrix.volume.windows }}\4.h2w'
 
       - run: '& .\f3read.exe -V'
       - run: '& .\f3read.exe --help'
-      - run: '& .\f3read.exe -s 2 -e 4 -r 50000 /cygdrive/c'
+      - run: '& .\f3read.exe -s 2 -e 4 -r 50000 ${{ matrix.volume.cygwin }}'
diff --git a/f3read.c b/f3read.c
index 12686f9..c52ef9a 100644
--- a/f3read.c
+++ b/f3read.c
@@ -438,6 +438,8 @@ int main(int argc, char **argv)
 	argp_parse(&argp, argc, argv, 0, NULL, &args);
 	print_header(stdout, "read");
 
+	adjust_dev_path(&args.dev_path);
+
 	files = ls_my_files(args.dev_path, args.start_at, args.end_at);
 
 	iterate_files(args.dev_path, files, args.start_at, args.end_at,
diff --git a/f3write.c b/f3write.c
index 112e7c6..c3cabed 100644
--- a/f3write.c
+++ b/f3write.c
@@ -372,6 +372,8 @@ int main(int argc, char **argv)
 	argp_parse(&argp, argc, argv, 0, NULL, &args);
 	print_header(stdout, "write");
 
+	adjust_dev_path(&args.dev_path);
+
 	unlink_old_files(args.dev_path, args.start_at, args.end_at);
 
 	return fill_fs(args.dev_path, args.start_at, args.end_at,
diff --git a/utils.c b/utils.c
index d32bcd7..3313ee8 100644
--- a/utils.c
+++ b/utils.c
@@ -18,10 +18,26 @@
 #include <dirent.h>
 #include <errno.h>
 #include <err.h>
+#include <unistd.h>
 
 #include "version.h"
 #include "utils.h"
 
+void adjust_dev_path(const char **dev_path)
+{
+	if (chdir(*dev_path)) {
+		err(errno, "Can't change working directory to %s at %s()", *dev_path, __func__);
+	}
+
+	if (!chroot(*dev_path)) {
+		assert(!chdir("/"));
+	} else if (errno != EPERM) {
+		err(errno, "Can't change root directory to %s at %s()", *dev_path, __func__);
+	}
+
+	*dev_path = ".";
+}
+
 const char *adjust_unit(double *ptr_bytes)
 {
 	const char *units[] = { "Byte", "KB", "MB", "GB", "TB", "PB", "EB" };
@@ -216,8 +232,6 @@ int posix_fadvise(int fd, off_t offset, off_t len, int advice)
 
 #if (__APPLE__ && __MACH__) || defined(__OpenBSD__)
 
-#include <unistd.h> /* For usleep(). */
-
 void msleep(double wait_ms)
 {
 	assert(!usleep(wait_ms * 1000));
diff --git a/utils.h b/utils.h
index ecbd0df..03031e2 100644
--- a/utils.h
+++ b/utils.h
@@ -9,6 +9,8 @@
 #define SECTOR_SIZE (512)
 #define GIGABYTES   (1024 * 1024 * 1024)
 
+void adjust_dev_path(const char **dev_path);
+
 const char *adjust_unit(double *ptr_bytes);
 
 /* Return true if @filename matches the regex /^[0-9]+\.h2w$/ */