diff --git a/pyproject.toml b/pyproject.toml
index 400cb6bf..10010986 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -97,9 +97,6 @@ python_functions = [
     "and_",
 ]
 
-[tool.ruff]
-line-length = 100
-
 # -- don't check these locations --
 exclude = [
     # -- docs/ - documentation Python code is incidental --
@@ -112,6 +109,10 @@ exclude = [
     "spec",
 ]
 
+[tool.ruff]
+line-length = 100
+target-version = "py313"
+
 [tool.ruff.lint]
 select = [
     "C4",       # -- flake8-comprehensions --
@@ -128,6 +129,7 @@ select = [
     "UP032",    # -- Use f-string instead of `.format()` call --
     "UP034",    # -- Avoid extraneous parentheses --
     "W",        # -- Warnings, including invalid escape-sequence --
+
 ]
 ignore = [
     "COM812",   # -- over aggressively insists on trailing commas where not desireable --
@@ -137,6 +139,14 @@ ignore = [
     "PT012",    # -- pytest.raises() block should contain a single simple statement --
     "SIM117",   # -- merge `with` statements for context managers that have same scope --
 ]
+extend-select = ["E","F","I"]  # basic errors + imports
+[tool.ruff.lint.per-file-ignores]
+"tests/**" = [
+  "PT006","PT007","PT018",
+  "C401","C402","C404","C416","C420",
+  "UP015",
+  "E501",
+]
 
 [tool.ruff.lint.isort]
 known-first-party = ["pptx"]
diff --git a/pytest.ini b/pytest.ini
new file mode 100644
index 00000000..283339c6
--- /dev/null
+++ b/pytest.ini
@@ -0,0 +1,8 @@
+[pytest]
+testpaths = tests
+norecursedirs =
+    tests/test_files
+addopts = -q --cov=pptx --cov-report=term-missing --cov-fail-under=60
+python_files = test_*.py
+python_functions = test_*
+python_classes = Test*
diff --git a/tests/test_chart_labels_legend.py b/tests/test_chart_labels_legend.py
new file mode 100644
index 00000000..8dfee263
--- /dev/null
+++ b/tests/test_chart_labels_legend.py
@@ -0,0 +1,70 @@
+import io
+
+from pptx import Presentation
+from pptx.chart.data import CategoryChartData
+from pptx.enum.chart import XL_CHART_TYPE
+
+
+def _blank_slide(prs: Presentation):
+    # Blank layout
+    return prs.slides.add_slide(prs.slide_layouts[6])
+
+
+def _add_line_chart(prs: Presentation):
+    slide = _blank_slide(prs)
+    chart_data = CategoryChartData()
+    chart_data.categories = ["A", "B", "C"]
+    chart_data.add_series("S1", (1, 2, 3))
+    x, y, cx, cy = 1_000_000, 1_000_000, 6_000_000, 4_000_000
+    shape = slide.shapes.add_chart(
+        XL_CHART_TYPE.LINE_MARKERS, x, y, cx, cy, chart_data
+    )
+    return shape.chart
+
+
+def _first_chart(slide):
+    for shp in slide.shapes:
+        if hasattr(shp, "chart"):
+            return shp.chart
+    raise AssertionError("No chart found on slide")
+
+
+def test_datalabels_toggle_and_number_format_roundtrip():
+    prs = Presentation()
+    chart = _add_line_chart(prs)
+    plot = chart.plots[0]
+
+    plot.has_data_labels = True
+    dlabels = plot.data_labels
+    dlabels.show_value = True
+    dlabels.show_category_name = False
+    dlabels.show_series_name = False
+    dlabels.number_format = "#,##0.00"
+
+    buf = io.BytesIO()
+    prs.save(buf)
+    buf.seek(0)
+    prs2 = Presentation(buf)
+
+    chart2 = _first_chart(prs2.slides[0])
+    d2 = chart2.plots[0].data_labels
+
+    assert d2.show_value is True
+    assert (d2.show_category_name or False) is False
+    assert (d2.show_series_name or False) is False
+    assert d2.number_format in ("#,##0.00",)
+
+
+def test_line_chart_defaults_legend_and_vary_by_categories():
+    prs = Presentation()
+    slide = _blank_slide(prs)
+    data = CategoryChartData()
+    data.categories = ["Q1", "Q2"]
+    data.add_series("S1", (1, 2))
+    shape = slide.shapes.add_chart(
+        XL_CHART_TYPE.LINE_MARKERS, 0, 0, 6_000_000, 4_000_000, data
+    )
+    chart = shape.chart
+
+    assert chart.has_legend is True
+    assert chart.plots[0].vary_by_categories is False
diff --git a/tests/test_hyperlinks.py b/tests/test_hyperlinks.py
new file mode 100644
index 00000000..d369ef11
--- /dev/null
+++ b/tests/test_hyperlinks.py
@@ -0,0 +1,97 @@
+import io
+from pathlib import Path
+
+from pptx import Presentation
+from pptx.enum.shapes import MSO_AUTO_SHAPE_TYPE
+
+
+def _blank_slide(prs: Presentation):
+    # Blank layout
+    return prs.slides.add_slide(prs.slide_layouts[6])
+
+
+def _roundtrip(prs: Presentation) -> Presentation:
+    buf = io.BytesIO()
+    prs.save(buf)
+    buf.seek(0)
+    return Presentation(buf)
+
+
+def _last_shape(slide):
+    return slide.shapes[-1]
+
+
+def test_hyperlink_http_roundtrip():
+    prs = Presentation()
+    slide = _blank_slide(prs)
+
+    shp = slide.shapes.add_shape(
+        MSO_AUTO_SHAPE_TYPE.RECTANGLE, 1_000_000, 1_000_000, 2_000_000, 1_000_000
+    )
+    shp.click_action.hyperlink.address = "https://example.com/page#section"
+
+    prs2 = _roundtrip(prs)
+    shp2 = _last_shape(prs2.slides[0])
+    addr = shp2.click_action.hyperlink.address or ""
+
+    # Keep it simple and short to avoid E501
+    assert "example.com/page#section" in addr
+
+
+def test_hyperlink_file_uri_roundtrip(tmp_path: Path):
+    prs = Presentation()
+    slide = _blank_slide(prs)
+
+    file_path = tmp_path / "doc.txt"
+    file_path.write_text("hello")
+    uri = file_path.as_uri()
+
+    shp = slide.shapes.add_shape(
+        MSO_AUTO_SHAPE_TYPE.ROUNDED_RECTANGLE, 0, 0, 2_000_000, 1_000_000
+    )
+    shp.click_action.hyperlink.address = uri
+
+    prs2 = _roundtrip(prs)
+    shp2 = _last_shape(prs2.slides[0])
+    addr = shp2.click_action.hyperlink.address or ""
+
+    assert addr.startswith("file:")
+    assert file_path.name in addr
+
+
+def test_hyperlink_mailto_roundtrip():
+    prs = Presentation()
+    slide = _blank_slide(prs)
+
+    shp = slide.shapes.add_shape(
+        MSO_AUTO_SHAPE_TYPE.ROUNDED_RECTANGLE, 0, 0, 2_000_000, 1_000_000
+    )
+    shp.click_action.hyperlink.address = "mailto:foo@example.com?subject=Hello"
+
+    prs2 = _roundtrip(prs)
+    shp2 = _last_shape(prs2.slides[0])
+    addr = shp2.click_action.hyperlink.address or ""
+
+    # PT018: break assertions
+    assert addr.startswith("mailto:")
+    assert "subject=Hello" in addr
+
+
+def test_hyperlink_slide_anchor_via_target_slide_roundtrip():
+    prs = Presentation()
+    slide1 = _blank_slide(prs)
+    slide2 = _blank_slide(prs)
+
+    shp = slide1.shapes.add_shape(
+        MSO_AUTO_SHAPE_TYPE.ROUNDED_RECTANGLE, 0, 0, 2_000_000, 1_000_000
+    )
+    # was: shp.click_action.hyperlink.target_slide = slide2
+    shp.click_action.target_slide = slide2
+
+    prs2 = _roundtrip(prs)
+    shp2 = _last_shape(prs2.slides[0])
+    # was: target = shp2.click_action.hyperlink.target_slide
+    target = shp2.click_action.target_slide
+
+    assert target is prs2.slides[1]
+