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test: mock network calls in altair chart dataframe tests #10188

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mscolnick merged 1 commit into from
Jul 16, 2026
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test: mock network calls in altair chart dataframe tests #10188

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23 changes: 19 additions & 4 deletions tests/_plugins/ui/_impl/test_altair_chart.py
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Original file line number Diff line number Diff line change
Expand Up @@ -777,8 +777,13 @@ def test_get_dataframe_csv() -> None:
import polars as pl

data = "https://cdn.jsdelivr.net/npm/vega-datasets@v1.29.0/data/stocks.csv"
chart = altair_chart(alt.Chart(data).mark_point().encode(x="values:Q"))
assert isinstance(chart.dataframe, (pd.DataFrame, pl.DataFrame))
fake_payload = b"symbol,price\nMSFT,39.81\nAAPL,28.13\n"

@cubic-dev-ai cubic-dev-ai Bot Jul 15, 2026

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P1: The unittest.mock.patch("urllib.request.urlopen", ...) in test_get_dataframe_csv() does not intercept the actual network call. When the chart data URL ends with .csv, the implementation in _get_dataframe_from_chart calls pl.read_csv(url) (or pd.read_csv(url)), both of which handle HTTP natively — they do not use urllib.request.urlopen. The mock is a no-op, so the test still makes a real HTTP request to the CDN.

This means the test (1) depends on external network availability, (2) will fail in airgapped or offline environments, and (3) defeats the PR's goal of mocking network calls.

To fix, either use a local file path or CSV string instead of a URL, or patch polars.read_csv / pandas.read_csv directly depending on which library the test environment provides.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At tests/_plugins/ui/_impl/test_altair_chart.py, line 780:

<comment>The `unittest.mock.patch("urllib.request.urlopen", ...)` in `test_get_dataframe_csv()` does not intercept the actual network call. When the chart data URL ends with `.csv`, the implementation in `_get_dataframe_from_chart` calls `pl.read_csv(url)` (or `pd.read_csv(url)`), both of which handle HTTP natively — they do **not** use `urllib.request.urlopen`. The mock is a no-op, so the test still makes a real HTTP request to the CDN.

This means the test (1) depends on external network availability, (2) will fail in airgapped or offline environments, and (3) defeats the PR's goal of mocking network calls.

To fix, either use a local file path or CSV string instead of a URL, or patch `polars.read_csv` / `pandas.read_csv` directly depending on which library the test environment provides.</comment>

<file context>
@@ -777,8 +777,13 @@ def test_get_dataframe_csv() -> None:
     data = "https://cdn.jsdelivr.net/npm/vega-datasets@v1.29.0/data/stocks.csv"
-    chart = altair_chart(alt.Chart(data).mark_point().encode(x="values:Q"))
-    assert isinstance(chart.dataframe, (pd.DataFrame, pl.DataFrame))
+    fake_payload = b"symbol,price\nMSFT,39.81\nAAPL,28.13\n"
+    with unittest.mock.patch(
+        "urllib.request.urlopen",
</file context>

with unittest.mock.patch(
"urllib.request.urlopen",
return_value=io.BytesIO(fake_payload),
):
chart = altair_chart(alt.Chart(data).mark_point().encode(x="values:Q"))
assert isinstance(chart.dataframe, (pd.DataFrame, pl.DataFrame))


@pytest.mark.skipif(not HAS_DEPS, reason="optional dependencies not installed")
Expand All @@ -790,8 +795,18 @@ def test_get_dataframe_json() -> None:
data = (
"https://cdn.jsdelivr.net/npm/vega-datasets@v1.29.0/data/barley.json"
)
chart = altair_chart(alt.Chart(data).mark_point().encode(x="values:Q"))
assert isinstance(chart.dataframe, (pd.DataFrame, pl.DataFrame))
fake_payload = json.dumps(
[
{"yield": 27.0, "variety": "Manchuria", "site": "University Farm"},
{"yield": 48.9, "variety": "Manchuria", "site": "Waseca"},
]
).encode("utf-8")
with unittest.mock.patch(
"urllib.request.urlopen",
return_value=io.BytesIO(fake_payload),
):
chart = altair_chart(alt.Chart(data).mark_point().encode(x="values:Q"))
assert isinstance(chart.dataframe, (pd.DataFrame, pl.DataFrame))


@pytest.mark.skipif(not HAS_DEPS, reason="optional dependencies not installed")
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