diff --git a/tests/multi_net/asyncio_tls_server_client.py b/tests/multi_net/asyncio_tls_server_client.py
index 996cdb3e0d..59e13ec45d 100644
--- a/tests/multi_net/asyncio_tls_server_client.py
+++ b/tests/multi_net/asyncio_tls_server_client.py
@@ -11,8 +11,8 @@ except ImportError:
 PORT = 8000
 
 # These are test certificates. See tests/README.md for details.
-cert = cafile = "multi_net/rsa_cert.der"
-key = "multi_net/rsa_key.der"
+cert = cafile = "rsa_cert.der"
+key = "rsa_key.der"
 
 try:
     os.stat(cafile)
diff --git a/tests/multi_net/asyncio_tls_server_client_cert_required_error.py b/tests/multi_net/asyncio_tls_server_client_cert_required_error.py
index bd4d7b82ea..8607e4ff10 100644
--- a/tests/multi_net/asyncio_tls_server_client_cert_required_error.py
+++ b/tests/multi_net/asyncio_tls_server_client_cert_required_error.py
@@ -11,8 +11,8 @@ except ImportError:
 PORT = 8000
 
 # These are test certificates. See tests/README.md for details.
-cert = cafile = "multi_net/rsa_cert.der"
-key = "multi_net/rsa_key.der"
+cert = cafile = "rsa_cert.der"
+key = "rsa_key.der"
 
 try:
     os.stat(cafile)
diff --git a/tests/multi_net/asyncio_tls_server_client_readline.py b/tests/multi_net/asyncio_tls_server_client_readline.py
index 28add38f5d..fd8685f5af 100644
--- a/tests/multi_net/asyncio_tls_server_client_readline.py
+++ b/tests/multi_net/asyncio_tls_server_client_readline.py
@@ -11,8 +11,8 @@ except ImportError:
 PORT = 8000
 
 # These are test certificates. See tests/README.md for details.
-cert = cafile = "multi_net/rsa_cert.der"
-key = "multi_net/rsa_key.der"
+cert = cafile = "rsa_cert.der"
+key = "rsa_key.der"
 
 try:
     os.stat(cafile)
diff --git a/tests/multi_net/asyncio_tls_server_client_verify_error.py b/tests/multi_net/asyncio_tls_server_client_verify_error.py
index 46a476addf..c600dcc2c8 100644
--- a/tests/multi_net/asyncio_tls_server_client_verify_error.py
+++ b/tests/multi_net/asyncio_tls_server_client_verify_error.py
@@ -11,8 +11,8 @@ except ImportError:
 PORT = 8000
 
 # These are test certificates. See tests/README.md for details.
-cert = cafile = "multi_net/rsa_cert.der"
-key = "multi_net/rsa_key.der"
+cert = cafile = "rsa_cert.der"
+key = "rsa_key.der"
 
 try:
     os.stat(cafile)
diff --git a/tests/multi_net/ssl_cert_rsa.py b/tests/multi_net/ssl_cert_rsa.py
index 71c9a34797..d148c8ebcf 100644
--- a/tests/multi_net/ssl_cert_rsa.py
+++ b/tests/multi_net/ssl_cert_rsa.py
@@ -10,8 +10,8 @@ except ImportError:
 PORT = 8000
 
 # These are test certificates. See tests/README.md for details.
-certfile = "multi_net/rsa_cert.der"
-keyfile = "multi_net/rsa_key.der"
+certfile = "rsa_cert.der"
+keyfile = "rsa_key.der"
 
 try:
     os.stat(certfile)
diff --git a/tests/multi_net/sslcontext_check_hostname_error.py b/tests/multi_net/sslcontext_check_hostname_error.py
index 94bd472767..ac39211b09 100644
--- a/tests/multi_net/sslcontext_check_hostname_error.py
+++ b/tests/multi_net/sslcontext_check_hostname_error.py
@@ -11,8 +11,8 @@ except ImportError:
 PORT = 8000
 
 # These are test certificates. See tests/README.md for details.
-cert = cafile = "multi_net/rsa_cert.der"
-key = "multi_net/rsa_key.der"
+cert = cafile = "rsa_cert.der"
+key = "rsa_key.der"
 
 try:
     os.stat(cafile)
diff --git a/tests/multi_net/sslcontext_getpeercert.py b/tests/multi_net/sslcontext_getpeercert.py
index c75a37952e..8748c1f78e 100644
--- a/tests/multi_net/sslcontext_getpeercert.py
+++ b/tests/multi_net/sslcontext_getpeercert.py
@@ -12,8 +12,8 @@ except ImportError:
 PORT = 8000
 
 # These are test certificates. See tests/README.md for details.
-cert = cafile = "multi_net/rsa_cert.der"
-key = "multi_net/rsa_key.der"
+cert = cafile = "rsa_cert.der"
+key = "rsa_key.der"
 
 try:
     os.stat(cafile)
diff --git a/tests/multi_net/sslcontext_server_client.py b/tests/multi_net/sslcontext_server_client.py
index 4d2ac06c58..c263ae31bb 100644
--- a/tests/multi_net/sslcontext_server_client.py
+++ b/tests/multi_net/sslcontext_server_client.py
@@ -11,8 +11,8 @@ except ImportError:
 PORT = 8000
 
 # These are test certificates. See tests/README.md for details.
-certfile = "multi_net/rsa_cert.der"
-keyfile = "multi_net/rsa_key.der"
+certfile = "rsa_cert.der"
+keyfile = "rsa_key.der"
 
 try:
     os.stat(certfile)
diff --git a/tests/multi_net/sslcontext_server_client_ciphers.py b/tests/multi_net/sslcontext_server_client_ciphers.py
index e2de4e6ad4..be7c332b4c 100644
--- a/tests/multi_net/sslcontext_server_client_ciphers.py
+++ b/tests/multi_net/sslcontext_server_client_ciphers.py
@@ -11,8 +11,8 @@ except ImportError:
 PORT = 8000
 
 # These are test certificates. See tests/README.md for details.
-cert = cafile = "multi_net/rsa_cert.der"
-key = "multi_net/rsa_key.der"
+cert = cafile = "rsa_cert.der"
+key = "rsa_key.der"
 
 try:
     os.stat(cafile)
diff --git a/tests/multi_net/sslcontext_server_client_files.py b/tests/multi_net/sslcontext_server_client_files.py
index 2c8af21d23..e1ea1b3aa8 100644
--- a/tests/multi_net/sslcontext_server_client_files.py
+++ b/tests/multi_net/sslcontext_server_client_files.py
@@ -11,8 +11,8 @@ except ImportError:
 PORT = 8000
 
 # These are test certificates. See tests/README.md for details.
-cert = cafile = "multi_net/rsa_cert.der"
-key = "multi_net/rsa_key.der"
+cert = cafile = "rsa_cert.der"
+key = "rsa_key.der"
 
 try:
     os.stat(cafile)
diff --git a/tests/multi_net/sslcontext_verify_error.py b/tests/multi_net/sslcontext_verify_error.py
index 4feb4ce983..4a7a6cfcc1 100644
--- a/tests/multi_net/sslcontext_verify_error.py
+++ b/tests/multi_net/sslcontext_verify_error.py
@@ -11,8 +11,8 @@ except ImportError:
 PORT = 8000
 
 # These are test certificates. See tests/README.md for details.
-cert = cafile = "multi_net/rsa_cert.der"
-key = "multi_net/rsa_key.der"
+cert = cafile = "rsa_cert.der"
+key = "rsa_key.der"
 
 try:
     os.stat(cafile)
diff --git a/tests/multi_net/sslcontext_verify_time_error.py b/tests/multi_net/sslcontext_verify_time_error.py
index 36711acfc8..e5dc496451 100644
--- a/tests/multi_net/sslcontext_verify_time_error.py
+++ b/tests/multi_net/sslcontext_verify_time_error.py
@@ -11,8 +11,8 @@ except ImportError:
 PORT = 8000
 
 # These are test certificates. See tests/README.md for details.
-cert = cafile = "multi_net/expired_cert.der"
-key = "multi_net/rsa_key.der"
+cert = cafile = "expired_cert.der"
+key = "rsa_key.der"
 
 try:
     os.stat(cafile)
diff --git a/tests/run-multitests.py b/tests/run-multitests.py
index 5ae8b8ea48..93a6d3844d 100755
--- a/tests/run-multitests.py
+++ b/tests/run-multitests.py
@@ -27,13 +27,15 @@ import pyboard
 
 if os.name == "nt":
     CPYTHON3 = os.getenv("MICROPY_CPYTHON3", "python3.exe")
-    MICROPYTHON = os.getenv(
-        "MICROPY_MICROPYTHON", test_dir + "/../ports/windows/build-standard/micropython.exe"
+    MICROPYTHON = os.path.abspath(
+        os.getenv(
+            "MICROPY_MICROPYTHON", test_dir + "/../ports/windows/build-standard/micropython.exe"
+        )
     )
 else:
     CPYTHON3 = os.getenv("MICROPY_CPYTHON3", "python3")
-    MICROPYTHON = os.getenv(
-        "MICROPY_MICROPYTHON", test_dir + "/../ports/unix/build-standard/micropython"
+    MICROPYTHON = os.path.abspath(
+        os.getenv("MICROPY_MICROPYTHON", test_dir + "/../ports/unix/build-standard/micropython")
     )
 
 # For diff'ing test output
@@ -155,6 +157,7 @@ class PyInstance:
 class PyInstanceSubProcess(PyInstance):
     def __init__(self, argv, env=None):
         self.argv = argv
+        self.cwd = None
         self.env = {n: v for n, v in (i.split("=") for i in env)} if env else None
         self.popen = None
         self.finished = True
@@ -163,8 +166,9 @@ class PyInstanceSubProcess(PyInstance):
         return self.argv[0].rsplit("/")[-1]
 
     def prepare_script_from_file(self, filename, prepend, append):
-        # Make tests run in an isolated environment (i.e. `import io` would
-        # otherwise get the `tests/io` directory).
+        # Make tests run in the directory of the test file, and in an isolated environment
+        # (i.e. `import io` would otherwise get the `tests/io` directory).
+        self.cwd = os.path.dirname(filename)
         remove_cwd_from_sys_path = b"import sys\nsys.path.remove('')\n\n"
         return remove_cwd_from_sys_path + super().prepare_script_from_file(
             filename, prepend, append
@@ -179,6 +183,7 @@ class PyInstanceSubProcess(PyInstance):
                 stdout=subprocess.PIPE,
                 stderr=subprocess.STDOUT,
                 input=script,
+                cwd=self.cwd,
                 env=self.env,
             )
             output = p.stdout
@@ -192,6 +197,7 @@ class PyInstanceSubProcess(PyInstance):
             stdin=subprocess.PIPE,
             stdout=subprocess.PIPE,
             stderr=subprocess.STDOUT,
+            cwd=self.cwd,
             env=self.env,
         )
         self.finished = False