diff --git a/testsuite/drivers/alr.py b/testsuite/drivers/alr.py
index 3e40ff625..8a86e2b22 100644
--- a/testsuite/drivers/alr.py
+++ b/testsuite/drivers/alr.py
@@ -4,15 +4,13 @@
 
 import os
 import os.path
-
+import re
 from shutil import copytree
-from e3.os.process import Run, quote_arg
+
 from e3.fs import mkdir
+from e3.os.process import Run, quote_arg
 from e3.testsuite.driver.classic import ProcessResult
 
-import re
-
-
 TESTSUITE_ROOT = os.path.dirname(os.path.dirname(
     os.path.abspath(__file__)))
 
@@ -530,4 +528,15 @@ def alr_builds_dir() -> str:
     """
     Return the path to the builds directory
     """
-    return os.path.join(alr_config_dir(), "cache", "builds")
\ No newline at end of file
+    return os.path.join(alr_config_dir(), "cache", "builds")
+
+
+def external_compiler_version() -> str:
+    """
+    Return the version of the external compiler
+    """
+    # Obtain available compilers
+    p = run_alr("toolchain")
+
+    # Capture version
+    return re.search("gnat_external ([0-9.]+)", p.out, re.MULTILINE).group(1)
\ No newline at end of file
diff --git a/testsuite/drivers/helpers.py b/testsuite/drivers/helpers.py
index 8112c09fa..353cd61e7 100644
--- a/testsuite/drivers/helpers.py
+++ b/testsuite/drivers/helpers.py
@@ -272,4 +272,4 @@ def __exit__(self, exc_type, exc_val, exc_tb):
         # Release the file lock
         import fcntl
         fcntl.flock(self.lock_file.fileno(), fcntl.LOCK_UN)
-        self.lock_file.close()
+        self.lock_file.close()
\ No newline at end of file
diff --git a/testsuite/tests/build/hashes/compiler-input/test.py b/testsuite/tests/build/hashes/compiler-input/test.py
index 7633bc40d..5a127ac36 100644
--- a/testsuite/tests/build/hashes/compiler-input/test.py
+++ b/testsuite/tests/build/hashes/compiler-input/test.py
@@ -4,8 +4,8 @@
 
 import sys
 
-from drivers.alr import run_alr, init_local_crate, alr_with
-from drivers.asserts import assert_match, match_solution
+from drivers.alr import external_compiler_version, run_alr, init_local_crate, alr_with
+from drivers.asserts import assert_match
 from drivers.builds import clear_builds_dir, hash_input
 
 
@@ -16,16 +16,36 @@ def check_hash(signature: str) -> None:
     assert_match(f".*{signature}.*", hash_input("crate_real"))
 
 
-run_alr("config", "--set", "--global", "dependencies.shared", "true")
+# The first test is to check that the external compiler is used when no
+# explicit compiler is selected.
 
-# Select the default preferred compiler, in this index is gnat_native=8888
-run_alr("toolchain", "--select")
+# Disable compiler selection, so the external is used
+run_alr("toolchain", "--disable-assistant")
+
+# Enable shared dependencies
+run_alr("config", "--set", "--global", "dependencies.shared", "true")
 
 # Init a crate without explicit compiler dependency
 init_local_crate("xxx")
 alr_with("crate_real")  # A regular crate in the index
 run_alr("update")       # Ensure the hash inputs are written to disk
 
+# Check the external compiler is in the hash inputs
+check_hash(f"version:gnat_external={external_compiler_version()}")
+
+
+# Next, check that selecting a compiler results in it being used
+
+# Select the default preferred compiler, in this index is gnat_native=8888
+run_alr("toolchain", "--select", "gnat_native")
+# Clear the build cache so we are able to locate the new hash
+clear_builds_dir()
+run_alr("update")
+run_alr("update")
+# Twice necessary because otherwise the hash inputs cannot be written (during
+# the first update the destination folder does not yet exist, and the crate
+# sync would remove the hash inputs file)
+
 # Check the expected compiler is in the hash inputs
 check_hash("version:gnat_native=8888.0.0")
 
@@ -33,7 +53,6 @@ def check_hash(signature: str) -> None:
 # Next, check with an explicit compiler in the dependencies. Note that we give
 # the virtual dependency, but the actual native one is used for the hash.
 
-# Clear the build cache so we are able to locate the new hash
 clear_builds_dir()
 alr_with("gnat=7777")  # Downgrade the compiler with an explicit dependency
 run_alr("update")