The tests use glibc's error.h, which musl libc does not implement.
Use err.h instead.

--- a/test-lm-big.c
+++ b/test-lm-big.c
@@ -19,7 +19,7 @@
 
 #include "test.h"
 #include <errno.h>
-#include <error.h>
+#include <err.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -107,7 +107,7 @@ main(int argc, char *argv[])
     /* Set the data. */
     r = luksmeta_save(cd, CRYPT_ANY_SLOT, UUID, DATA, sizeof(DATA));
     if (r < 0)
-        error(EXIT_FAILURE, -r, "luksmeta_save()");
+        err(EXIT_FAILURE, "luksmeta_save()");
 
     assert(test_layout((range_t[]) {
         { 0, 1024 },                   /* LUKS header */
--- a/test-lm-init.c
+++ b/test-lm-init.c
@@ -22,7 +22,7 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <errno.h>
-#include <error.h>
+#include <err.h>
 #include <stdio.h>
 #include <stdlib.h>
 
@@ -89,11 +89,11 @@ main(int argc, char *argv[])
     /* Test to make sure that data corruption is picked up correctly. */
     fd = open(filename, O_RDWR | O_SYNC);
     if (fd < 0)
-        error(EXIT_FAILURE, errno, "%s:%d", __FILE__, __LINE__);
+        err(EXIT_FAILURE, "%s:%d", __FILE__, __LINE__);
     if (lseek(fd, offset + 16, SEEK_SET) == -1)
-        error(EXIT_FAILURE, errno, "%s:%d", __FILE__, __LINE__);
+        err(EXIT_FAILURE, "%s:%d", __FILE__, __LINE__);
     if (write(fd, &(char) { 17 }, 1) != 1)
-        error(EXIT_FAILURE, errno, "%s:%d", __FILE__, __LINE__);
+        err(EXIT_FAILURE, "%s:%d", __FILE__, __LINE__);
     close(fd);
     assert(luksmeta_save(cd, 2, UUID, UUID, sizeof(UUID)) == -EINVAL);
     assert(luksmeta_load(cd, 2, uuid, data, sizeof(data)) == -EINVAL);
--- a/test-lm-one.c
+++ b/test-lm-one.c
@@ -18,7 +18,7 @@
  */
 
 #include "test.h"
-#include <error.h>
+#include <err.h>
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
@@ -44,7 +44,7 @@ main(int argc, char *argv[])
 
     r = luksmeta_save(cd, CRYPT_ANY_SLOT, UUID, UUID, sizeof(UUID));
     if (r < 0)
-        error(EXIT_FAILURE, -r, "%s:%d", __FILE__, __LINE__);
+        err(EXIT_FAILURE, "%s:%d", __FILE__, __LINE__);
 
     /* Test the layout state. */
     assert(test_layout((range_t[]) {
--- a/test-lm-two.c
+++ b/test-lm-two.c
@@ -18,7 +18,7 @@
  */
 
 #include "test.h"
-#include <error.h>
+#include <err.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -49,7 +49,7 @@ main(int argc, char *argv[])
     /* Add one metadata. */
     r = luksmeta_save(cd, 0, UUID0, UUID0, sizeof(UUID0));
     if (r < 0)
-        error(EXIT_FAILURE, -r, "luksmeta_save()");
+        err(EXIT_FAILURE, "luksmeta_save()");
 
     assert(test_layout((range_t[]) {
         { 0, 1024 },                   /* LUKS header */
@@ -66,7 +66,7 @@ main(int argc, char *argv[])
     /* Add a second metadata. */
     r = luksmeta_save(cd, 1, UUID1, UUID1, sizeof(UUID1));
     if (r < 0)
-        error(EXIT_FAILURE, -r, "luksmeta_save()");
+        err(EXIT_FAILURE, "luksmeta_save()");
 
     assert(test_layout((range_t[]) {
         { 0, 1024 },                   /* LUKS header */
--- a/test.c
+++ b/test.c
@@ -18,7 +18,7 @@
  */
 
 #include <assert.h>
-#include <error.h>
+#include <err.h>
 #include <errno.h>
 #include <stdbool.h>
 #include <stdio.h>
@@ -105,7 +105,7 @@ test_hole(struct crypt_device *cd, uint32_t *offset, uint32_t *length)
 
     payload_offset = crypt_get_data_offset(cd) * 512;
     if (payload_offset < ALIGN(1, true))
-        error(EXIT_FAILURE, -r, "%s:%d", __FILE__, __LINE__);
+        err(EXIT_FAILURE, "%s:%d", __FILE__, __LINE__);
 
     for (int slot = 0; slot < crypt_keyslot_max(CRYPT_LUKS1); slot++) {
         uint64_t off = 0;
@@ -113,7 +113,7 @@ test_hole(struct crypt_device *cd, uint32_t *offset, uint32_t *length)
 
         r = crypt_keyslot_area(cd, slot, &off, &len);
         if (r < 0)
-            error(EXIT_FAILURE, -r, "%s:%d", __FILE__, __LINE__);
+            err(EXIT_FAILURE, "%s:%d", __FILE__, __LINE__);
 
         if (off + len > keyarea_end)
             keyarea_end = off + len;
@@ -132,23 +132,23 @@ test_format(void)
 
     fd = mkstemp(filename);
     if (fd < 0)
-        error(EXIT_FAILURE, errno, "%s:%d", __FILE__, __LINE__);
+        err(EXIT_FAILURE, "%s:%d", __FILE__, __LINE__);
 
     /* Create a 4MB sparse file. */
     if (lseek(fd, 4194303, SEEK_SET) == -1)
-        error(EXIT_FAILURE, errno, "%s:%d", __FILE__, __LINE__);
+        err(EXIT_FAILURE, "%s:%d", __FILE__, __LINE__);
     if (write(fd, "", 1) != 1)
-        error(EXIT_FAILURE, errno, "%s:%d", __FILE__, __LINE__);
+        err(EXIT_FAILURE, "%s:%d", __FILE__, __LINE__);
     close(fd);
 
     r = crypt_init(&cd, filename);
     if (r < 0)
-        error(EXIT_FAILURE, -r, "%s:%d", __FILE__, __LINE__);
+        err(EXIT_FAILURE, "%s:%d", __FILE__, __LINE__);
 
     r = crypt_format(cd, CRYPT_LUKS1, "aes", "xts-plain64",
                      NULL, NULL, 32, NULL);
     if (r < 0)
-        error(EXIT_FAILURE, -r, "%s:%d", __FILE__, __LINE__);
+        err(EXIT_FAILURE,  "%s:%d", __FILE__, __LINE__);
 
     return cd;
 }
@@ -161,15 +161,15 @@ test_init(void)
 
     r = crypt_init(&cd, filename);
     if (r < 0)
-        error(EXIT_FAILURE, -r, "%s:%d", __FILE__, __LINE__);
+        err(EXIT_FAILURE, "%s:%d", __FILE__, __LINE__);
 
     r = crypt_load(cd, CRYPT_LUKS1, NULL);
     if (r < 0)
-        error(EXIT_FAILURE, -r, "%s:%d", __FILE__, __LINE__);
+        err(EXIT_FAILURE, "%s:%d", __FILE__, __LINE__);
 
     r = luksmeta_init(cd);
     if (r < 0)
-        error(EXIT_FAILURE, -r, "%s:%d", __FILE__, __LINE__);
+        err(EXIT_FAILURE, "%s:%d", __FILE__, __LINE__);
 
     return cd;
 }