Ensure our histogram uses a non-zero step

docs/news/113.bugfix.rst

@@ -0,0 +1 @@
+Fix the generation of histograms when the tests performed zero-byte allocations.

src/pytest_memray/plugin.py

@@ -78,7 +78,7 @@ def histogram(
     [0, 0, 0, 0, 1, 0, 0, 1, 3, 2]
 
     """
-    step = ((high - low) / bins) or low
+    step = ((high - low) / bins) or low or 1
     dist = collections.Counter((x - low) // step for x in iterable)
     return [dist[b] for b in range(bins)]
 
@@ -91,7 +91,7 @@ def cli_hist(data: Iterable[float], bins: int, *, log_scale: bool = True) -> str
     high = max(data)
     data_bins = histogram(data, low=low, high=high, bins=bins)
     bar_indexes = (int(elem * (len(bars) - 1) / max(data_bins)) for elem in data_bins)
-    result = " ".join(bars[bar_index] for bar_index in bar_indexes)
+    result = "".join(bars[bar_index] for bar_index in bar_indexes)
     return result
 
 

tests/test_utils.py

@@ -15,6 +15,7 @@
 
 from pytest_memray.utils import WriteEnabledDirectoryAction
 from pytest_memray.utils import parse_memory_string
+from pytest_memray.plugin import cli_hist
 
 
 @pytest.mark.parametrize(
@@ -123,3 +124,25 @@ def test_write_enabled_dir_cannot_create(
             w_dir_check(path)
     finally:
         tmp_path.chmod(tmp_path.stat().st_mode | write)
+
+
+def test_histogram_with_zero_byte_allocations():
+    # GIVEN
+    allocations = [0, 100, 990, 1000, 50000]
+
+    # WHEN
+    histogram = cli_hist(allocations, bins=5)
+
+    # THEN
+    assert histogram == "▄ ▄█▄"
+
+
+def test_histogram_with_only_zero_byte_allocations():
+    # GIVEN
+    allocations = [0, 0, 0, 0]
+
+    # WHEN
+    histogram = cli_hist(allocations, bins=5)
+
+    # THEN
+    assert histogram == "█    "