diff --git a/tests/common b/tests/common
index c45701e..5abe951 100644
--- a/tests/common
+++ b/tests/common
@@ -7,6 +7,13 @@ SWTPM_SETUP=${SWTPM_SETUP:-${ROOT}/src/swtpm_setup/swtpm_setup}
 SWTPM_CERT=${SWTPM_CERT:-${ROOT}/src/swtpm_cert/swtpm_cert}
 ECHO=$(type -P echo)
 
+case "$(uname -s)" in
+Darwin)
+	CERTTOOL=gnutls-certtool;;
+*)
+	CERTTOOL=certtool;;
+esac
+
 # Note: Do not use file descriptors above 127 due to OpenBSD.
 
 # Kill a process quietly
diff --git a/tests/test_samples_create_tpmca b/tests/test_samples_create_tpmca
index 66d9ac6..538d287 100755
--- a/tests/test_samples_create_tpmca
+++ b/tests/test_samples_create_tpmca
@@ -76,13 +76,6 @@ function cleanup()
 trap "cleanup" SIGTERM EXIT
 source ${TESTDIR}/common
 
-case "$(uname -s)" in
-Darwin)
-	CERTTOOL=gnutls-certtool;;
-*)
-	CERTTOOL=certtool;;
-esac
-
 PATH=${ROOT}/src/swtpm_bios:${ROOT}/src/swtpm_cert:${PATH}
 
 # run the test with the given owner and SRK passwords
diff --git a/tests/test_tpm2_samples_create_tpmca b/tests/test_tpm2_samples_create_tpmca
index fd9c658..8af3098 100755
--- a/tests/test_tpm2_samples_create_tpmca
+++ b/tests/test_tpm2_samples_create_tpmca
@@ -85,13 +85,6 @@ function cleanup()
 trap "cleanup" SIGTERM EXIT
 source ${TESTDIR}/common
 
-case "$(uname -s)" in
-Darwin)
-	CERTTOOL=gnutls-certtool;;
-*)
-	CERTTOOL=certtool;;
-esac
-
 PATH=${ROOT}/src/swtpm_bios:${ROOT}/src/swtpm_cert:${PATH}
 
 # Run the tests
diff --git a/tests/test_tpm2_samples_swtpm_localca b/tests/test_tpm2_samples_swtpm_localca
index 4f1193f..3954b75 100755
--- a/tests/test_tpm2_samples_swtpm_localca
+++ b/tests/test_tpm2_samples_swtpm_localca
@@ -22,6 +22,8 @@ CERTSERIAL=${workdir}/certserial
 
 PATH=${TOPBUILD}/src/swtpm_cert:$PATH
 
+source ${TESTDIR}/common
+
 trap "cleanup" SIGTERM EXIT
 
 function cleanup()
@@ -29,13 +31,6 @@ function cleanup()
 	rm -rf "${workdir}"
 }
 
-case "$(uname -s)" in
-Darwin)
-	CERTTOOL=gnutls-certtool;;
-*)
-	CERTTOOL=certtool;;
-esac
-
 cat <<_EOF_ > "${workdir}/swtpm-localca.conf"
 statedir=${workdir}
 signingkey = ${SIGNINGKEY}
diff --git a/tests/test_tpm2_samples_swtpm_localca_pkcs11 b/tests/test_tpm2_samples_swtpm_localca_pkcs11
index 16084be..fa23da1 100755
--- a/tests/test_tpm2_samples_swtpm_localca_pkcs11
+++ b/tests/test_tpm2_samples_swtpm_localca_pkcs11
@@ -33,6 +33,8 @@ CERTSERIAL=${workdir}/certserial
 
 PATH=${TOPBUILD}/src/swtpm_cert:$PATH
 
+source ${TESTDIR}/common
+
 trap "cleanup" SIGTERM EXIT
 
 function cleanup()
@@ -41,13 +43,6 @@ function cleanup()
 	${TESTDIR}/softhsm_setup teardown
 }
 
-case "$(uname -s)" in
-Darwin)
-	CERTTOOL=gnutls-certtool;;
-*)
-	CERTTOOL=certtool;;
-esac
-
 unset GNUTLS_PIN
 export PIN="abcdef"
 
diff --git a/tests/test_tpm2_save_load_state_3 b/tests/test_tpm2_save_load_state_3
index e565212..a37d15b 100755
--- a/tests/test_tpm2_save_load_state_3
+++ b/tests/test_tpm2_save_load_state_3
@@ -49,13 +49,6 @@ source ${TESTDIR}/common
 
 trap "cleanup" SIGTERM EXIT
 
-case "$(uname -s)" in
-Darwin)
-	CERTTOOL=gnutls-certtool;;
-*)
-	CERTTOOL=certtool;;
-esac
-
 function cleanup()
 {
 	rm -rf $TPMDIR