diff --git a/src/sparsemap.c b/src/sparsemap.c
index 67e8b14..34c57a3 100644
--- a/src/sparsemap.c
+++ b/src/sparsemap.c
@@ -114,7 +114,7 @@ typedef struct {
   sm_bitvec_t *m_data;
 } __sm_chunk_t;
 
-struct sparsemap {
+struct __attribute__((aligned(8))) sparsemap {
   uint8_t *m_data;    /* The serialized bitmap data */
   size_t m_capacity;  /* The total size of m_data */
   size_t m_data_used; /* The used size of m_data */
@@ -764,19 +764,13 @@ __sm_append_data(sparsemap_t *map, uint8_t *buffer, size_t buffer_size)
 /**
  * Inserts data somewhere in the middle of m_data.
  */
-static int
+void
 __sm_insert_data(sparsemap_t *map, size_t offset, uint8_t *buffer, size_t buffer_size)
 {
-  if (map->m_data_used + buffer_size > map->m_capacity) {
-    __sm_assert(!"buffer overflow");
-    abort();
-  }
-
   uint8_t *p = __sm_get_chunk_map_data(map, offset);
   memmove(p + buffer_size, p, map->m_data_used - offset);
   memcpy(p, buffer, buffer_size);
   map->m_data_used += buffer_size;
-  return 0;
 }
 
 /**
@@ -944,6 +938,11 @@ sparsemap_set(sparsemap_t *map, sparsemap_idx_t idx, bool value)
   ssize_t offset = __sm_get_chunk_map_offset(map, idx);
   bool dont_grow = false;
 
+  if (map->m_data_used + sizeof(sm_idx_t) + sizeof(sm_bitvec_t) * 2 > map->m_capacity) {
+    errno = ENOSPC;
+    return SPARSEMAP_IDX_MAX;
+  }
+
   /* If there is no __sm_chunk_t and the bit is set to zero then return
      immediately; otherwise create an initial __sm_chunk_t. */
   if (offset == -1) {
@@ -959,8 +958,8 @@ sparsemap_set(sparsemap_t *map, sparsemap_idx_t idx, bool value)
 
     __sm_set_chunk_map_count(map, 1);
 
-    /* We already inserted an additional sm_bitvec_t; later on there
-       is no need to grow the vector even further. */
+    /* We already inserted an additional sm_bitvec_t; given that has happened
+       there is no need to grow the vector even further. */
     dont_grow = true;
     offset = 0;
   }
@@ -1044,8 +1043,10 @@ sparsemap_set(sparsemap_t *map, sparsemap_idx_t idx, bool value)
       offset += (ssize_t)(sizeof(sm_idx_t) + position * sizeof(sm_bitvec_t));
       __sm_insert_data(map, offset, (uint8_t *)&fill, sizeof(sm_bitvec_t));
     }
-    code = __sm_chunk_map_set(&chunk, idx - start, value, &position, &fill, true);
-    __sm_assert(code == SM_OK);
+    __sm_when_diag({
+	code = __sm_chunk_map_set(&chunk, idx - start, value, &position, &fill, true);
+	__sm_assert(code == SM_OK);
+      });
     break;
   case SM_NEEDS_TO_SHRINK:
     /* If the __sm_chunk_t is empty then remove it. */
@@ -1259,12 +1260,9 @@ sparsemap_select(sparsemap_t *map, sparsemap_idx_t n, bool value)
 
       p += __sm_chunk_map_get_size(&chunk);
     }
-#ifdef DEBUG
-    assert(!"shouldn't be here");
-#endif
-    return SPARSEMAP_IDX_MAX;
+    return SPARSEMAP_IDX_MAX; // TODO... shouldn't be here?
   } else {
-    return SPARSEMAP_IDX_MIN; // TODO... sparsemap_select(map, -n, value);
+    return SPARSEMAP_IDX_MIN; // TODO... sparsemap_select(map, -n, value); seek from end, not start
   }
 }
 
diff --git a/tests/common.c b/tests/common.c
index 01b2ae7..4a9baed 100644
--- a/tests/common.c
+++ b/tests/common.c
@@ -118,7 +118,7 @@ has_sequential_set(int a[], int l, int r)
 int
 ensure_sequential_set(int a[], int l, int r)
 {
-  if (!a || l == 0 || r < 1 || r > l) {
+  if (!a || l == 0 || r < 1 || r > l - 1) {
     return 0;
   }
 
diff --git a/tests/test.c b/tests/test.c
index 2fc93f2..6166e8a 100644
--- a/tests/test.c
+++ b/tests/test.c
@@ -314,20 +314,23 @@ test_api_remaining_capacity(const MunitParameter params[], void *data)
   do {
     sparsemap_set(map, i++, true);
     cap = sparsemap_capacity_remaining(map);
-  } while (cap > 1.0);
-  // assert_true(i == 169985); when seed is 8675309
-  assert_true(cap <= 1.0);
+  } while (cap > 1.0 && errno != ENOSPC);
+  errno = 0;
+  assert_true(cap <= 2.0);
 
   sparsemap_clear(map);
+  cap = sparsemap_capacity_remaining(map);
+  assert_true(cap > 99);
+
   i = 0;
   do {
     int p = munit_rand_int_range(0, 150000);
     sparsemap_set(map, p, true);
     i++;
     cap = sparsemap_capacity_remaining(map);
-  } while (cap > 2.0);
-  // assert_true(i == 64); when seed is 8675309
-  assert_true(cap <= 2.0);
+  } while (cap > 1.0 && errno != ENOSPC);
+  errno = 0;
+  assert_true(cap <= 1.0);
 
   return MUNIT_OK;
 }
@@ -873,33 +876,32 @@ static MunitTest api_test_suite[] = {
 static void *
 test_scale_lots_o_spans_setup(const MunitParameter params[], void *user_data)
 {
-  uint8_t *buf = munit_calloc(10 * 1024, sizeof(uint8_t));
-  assert_ptr_not_null(buf);
-  sparsemap_t *map = (sparsemap_t *)test_api_setup(params, user_data);
-
-  sparsemap_init(map, buf, 10 * 1024);
-
+  (void)params;
+  (void)user_data;
+  sparsemap_t *map = sparsemap(10 * 1024);
+  assert_ptr_not_null(map);
   return (void *)map;
 }
 static void
 test_scale_lots_o_spans_tear_down(void *fixture)
 {
   sparsemap_t *map = (sparsemap_t *)fixture;
-  assert_ptr_not_null(map->m_data);
-  munit_free(map->m_data);
-  test_api_tear_down(fixture);
+  assert_ptr_not_null(map);
+  munit_free(map);
 }
 static MunitResult
 test_scale_lots_o_spans(const MunitParameter params[], void *data)
 {
+  size_t amt = 897915; // 268435456
   sparsemap_t *map = (sparsemap_t *)data;
   (void)params;
 
   assert_ptr_not_null(map);
 
-  for (int i = 0; i < 268435456;) {
+  for (size_t i = 0; i < amt;) {
     int l = i % 31 + 16;
-    sm_add_span(map, 268435456, l);
+    // TODO: sm_add_span(map, amt, l);
+    sm_add_span(map, 10000, l);
     if (errno == ENOSPC) {
       map = sparsemap_set_data_size(map, sparsemap_get_capacity(map) * 2);
       errno = 0;
@@ -908,7 +910,6 @@ test_scale_lots_o_spans(const MunitParameter params[], void *data)
     /* ANSI esc code to clear line, carrage return, then print on the same line */
     // printf("\033[2K\r%d", i);
     // printf("%d\t%d\n", l, i);
-    // fflush(stdout);
   }
 
   return MUNIT_OK;
@@ -917,21 +918,18 @@ test_scale_lots_o_spans(const MunitParameter params[], void *data)
 static void *
 test_scale_ondrej_setup(const MunitParameter params[], void *user_data)
 {
-  uint8_t *buf = munit_calloc(1024, sizeof(uint8_t));
-  assert_ptr_not_null(buf);
-  sparsemap_t *map = (sparsemap_t *)test_api_setup(params, user_data);
-
-  sparsemap_init(map, buf, 1024);
-
+  (void)params;
+  (void)user_data;
+  sparsemap_t *map = sparsemap(10 * 1024);
+  assert_ptr_not_null(map);
   return (void *)map;
 }
 static void
 test_scale_ondrej_tear_down(void *fixture)
 {
   sparsemap_t *map = (sparsemap_t *)fixture;
-  assert_ptr_not_null(map->m_data);
-  munit_free(map->m_data);
-  test_api_tear_down(fixture);
+  assert_ptr_not_null(map);
+  munit_free(map);
 }
 static MunitResult
 test_scale_ondrej(const MunitParameter params[], void *data)
@@ -948,59 +946,49 @@ test_scale_ondrej(const MunitParameter params[], void *data)
     for (sparsemap_idx_t j = 0; j < stride; j++) {
       bool set = (i != needle) ? (j < 10) : (j < 9);
       sparsemap_set(map, i, set);
+      if (errno == ENOSPC) {
+        map = sparsemap_set_data_size(map, sparsemap_get_capacity(map) * 2);
+        errno = 0;
+      }
     }
   }
-#if 0
-  //  sm_add_span(map, 268435456, 9);
-
-  size_t b = sparsemap_span(map, 0, 8, true);
-  if (SPARSEMAP_NOT_FOUND(b)) {
-    printf("%ld\n", b);
-    printf("%ld / %ld == %ld %ld\n", b, stride, b / stride, needle);
-  } else {
-    printf("not found\n");
-  }
-  /*
-  size_t b = sparsemap_span(map, 0, 9, false); TODO
-  printf("%ld (%d) / %d == %d", b, (int)b, stride, needle);
-  fflush(stdout);
-  assert_true(((int)b / stride) == needle);
-  */
-#endif
+  sparsemap_idx_t a = sparsemap_span(map, 0, 9, false);
+  assert_true((a / stride) == needle);
   return MUNIT_OK;
 }
 
 static void *
 test_scale_spans_come_spans_go_setup(const MunitParameter params[], void *user_data)
 {
-  uint8_t *buf = munit_calloc(1024, sizeof(uint8_t));
-  assert_ptr_not_null(buf);
-  sparsemap_t *map = (sparsemap_t *)test_api_setup(params, user_data);
-
-  sparsemap_init(map, buf, 1024);
-
+  (void)params;
+  (void)user_data;
+  sparsemap_t *map = sparsemap(10 * 1024);
+  assert_ptr_not_null(map);
   return (void *)map;
 }
 static void
 test_scale_spans_come_spans_go_tear_down(void *fixture)
 {
   sparsemap_t *map = (sparsemap_t *)fixture;
-  assert_ptr_not_null(map->m_data);
-  munit_free(map->m_data);
-  test_api_tear_down(fixture);
+  assert_ptr_not_null(map);
+  munit_free(map);
 }
 static MunitResult
 test_scale_spans_come_spans_go(const MunitParameter params[], void *data)
 {
+  size_t amt = 897915; // 268435456, ~5e7 interations due to 2e9 / avg(l)
   sparsemap_t *map = (sparsemap_t *)data;
   (void)params;
 
   assert_ptr_not_null(map);
 
-  /* ~5e7 interations due to 2e9 / avg(l) */
-  for (int i = 0; i < 268435456;) {
+  for (size_t i = 0; i < amt;) {
     int l = i % 31 + 16;
-    sm_add_span(map, 268435456, l);
+    sm_add_span(map, amt, l);
+    if (errno == ENOSPC) {
+      map = sparsemap_set_data_size(map, sparsemap_get_capacity(map) * 2);
+      errno = 0;
+    }
 
     /* After 10,000 spans are in there we consume a span every iteration. */
     if (l > 10000) {
@@ -1069,7 +1057,6 @@ test_scale_best_case(const MunitParameter params[], void *data)
   for (int i = 0; i < 172032; i++) {
     /* ANSI esc code to clear line, carrage return, then print on the same line */
     //    printf("\033[2K\r%d", i);
-    //    fflush(stdout);
     sparsemap_set(map, i, true);
   }
 
@@ -1116,7 +1103,6 @@ test_scale_worst_case(const MunitParameter params[], void *data)
   for (int i = 0; i < 7744; i += 2) {
     /* ANSI esc code to clear line, carrage return, then print on the same line */
     //    printf("\033[2K\r%d", i);
-    //    fflush(stdout);
     sparsemap_set(map, i, true);
   }
 
@@ -1260,6 +1246,11 @@ int
 main(int argc, char *argv[MUNIT_ARRAY_PARAM(argc + 1)])
 {
   struct user_data info;
+
+  /* Disable buffering on std{out,err} to avoid having to call fflush(). */
+  setvbuf(stdout, NULL, _IONBF, 0);
+  setvbuf(stderr, NULL, _IONBF, 0);
+
   return munit_suite_main(&main_test_suite, (void *)&info, argc, argv);
 }