Refactor DataFrame tests. (#10204)

This PR refactors some DataFrame tests, including [suggestions](#10141 (comment)) from @vyasr in #10141 that are not related to that PR's focus.

Authors:
  - Bradley Dice (https://github.com/bdice)

Approvers:
  - GALI PREM SAGAR (https://github.com/galipremsagar)

URL: #10204

python/cudf/cudf/tests/test_dataframe.py

@@ -246,17 +246,15 @@ def test_series_init_none():
     sr1 = cudf.Series()
     got = sr1.to_string()
 
-    expect = sr1.to_pandas().__repr__()
-    # values should match despite whitespace difference
-    assert got.split() == expect.split()
+    expect = repr(sr1.to_pandas())
+    assert got == expect
 
     # 2: Using `None` as an initializer
     sr2 = cudf.Series(None)
     got = sr2.to_string()
 
-    expect = sr2.to_pandas().__repr__()
-    # values should match despite whitespace difference
-    assert got.split() == expect.split()
+    expect = repr(sr2.to_pandas())
+    assert got == expect
 
 
 def test_dataframe_basic():
@@ -843,31 +841,29 @@ def test_dataframe_to_string_with_masked_data():
 def test_dataframe_to_string_wide(monkeypatch):
     monkeypatch.setenv("COLUMNS", "79")
     # Test basic
-    df = cudf.DataFrame()
-    for i in range(100):
-        df["a{}".format(i)] = list(range(3))
-    pd.options.display.max_columns = 0
-    got = df.to_string()
+    df = cudf.DataFrame({f"a{i}": [0, 1, 2] for i in range(100)})
+    with pd.option_context("display.max_columns", 0):
+        got = df.to_string()
 
-    expect = """
-    a0  a1  a2  a3  a4  a5  a6  a7 ...  a92 a93 a94 a95 a96 a97 a98 a99
-0    0   0   0   0   0   0   0   0 ...    0   0   0   0   0   0   0   0
-1    1   1   1   1   1   1   1   1 ...    1   1   1   1   1   1   1   1
-2    2   2   2   2   2   2   2   2 ...    2   2   2   2   2   2   2   2
-[3 rows x 100 columns]
-"""
-    # values should match despite whitespace difference
-    assert got.split() == expect.split()
+    expect = textwrap.dedent(
+        """\
+           a0  a1  a2  a3  a4  a5  a6  a7  ...  a92  a93  a94  a95  a96  a97  a98  a99
+        0   0   0   0   0   0   0   0   0  ...    0    0    0    0    0    0    0    0
+        1   1   1   1   1   1   1   1   1  ...    1    1    1    1    1    1    1    1
+        2   2   2   2   2   2   2   2   2  ...    2    2    2    2    2    2    2    2
+
+        [3 rows x 100 columns]"""  # noqa: E501
+    )
+    assert got == expect
 
 
 def test_dataframe_empty_to_string():
     # Test for printing empty dataframe
     df = cudf.DataFrame()
     got = df.to_string()
 
-    expect = "Empty DataFrame\nColumns: []\nIndex: []\n"
-    # values should match despite whitespace difference
-    assert got.split() == expect.split()
+    expect = "Empty DataFrame\nColumns: []\nIndex: []"
+    assert got == expect
 
 
 def test_dataframe_emptycolumns_to_string():
@@ -877,9 +873,8 @@ def test_dataframe_emptycolumns_to_string():
     df["b"] = []
     got = df.to_string()
 
-    expect = "Empty DataFrame\nColumns: [a, b]\nIndex: []\n"
-    # values should match despite whitespace difference
-    assert got.split() == expect.split()
+    expect = "Empty DataFrame\nColumns: [a, b]\nIndex: []"
+    assert got == expect
 
 
 def test_dataframe_copy():
@@ -890,14 +885,14 @@ def test_dataframe_copy():
     df2["b"] = [4, 5, 6]
     got = df.to_string()
 
-    expect = """
-     a
-0    1
-1    2
-2    3
-"""
-    # values should match despite whitespace difference
-    assert got.split() == expect.split()
+    expect = textwrap.dedent(
+        """\
+           a
+        0  1
+        1  2
+        2  3"""
+    )
+    assert got == expect
 
 
 def test_dataframe_copy_shallow():
@@ -908,14 +903,14 @@ def test_dataframe_copy_shallow():
     df2["b"] = [4, 2, 3]
     got = df.to_string()
 
-    expect = """
-     a
-0    1
-1    2
-2    3
-"""
-    # values should match despite whitespace difference
-    assert got.split() == expect.split()
+    expect = textwrap.dedent(
+        """\
+           a
+        0  1
+        1  2
+        2  3"""
+    )
+    assert got == expect
 
 
 def test_dataframe_dtypes():