[tests] Refactor the test files for BigDecimal

src/decimojo/__init__.mojo

@@ -29,7 +29,14 @@ from .decimal.decimal import Decimal, Dec
 from .bigint.bigint import BigInt, BInt
 from .biguint.biguint import BigUInt, BUInt
 from .bigdecimal.bigdecimal import BigDecimal, BigDec, BDec
-from .rounding_mode import RoundingMode, RM
+from .rounding_mode import (
+    RoundingMode,
+    RM,
+    ROUND_DOWN,
+    ROUND_HALF_UP,
+    ROUND_HALF_EVEN,
+    ROUND_UP,
+)
 
 # Core functions
 from .decimal.arithmetics import (

src/decimojo/bigdecimal/bigdecimal.mojo

@@ -739,9 +739,30 @@ struct BigDecimal(
         return decimojo.bigdecimal.exponential.power(self, exponent, precision)
 
     @always_inline
-    fn round(self, ndigits: Int, rounding_mode: RoundingMode) raises -> Self:
-        """Rounds the number to the specified precision.
-        See `bigdecimal.rounding.round()` for more information.
+    fn round(
+        self,
+        ndigits: Int,
+        rounding_mode: RoundingMode = RoundingMode.ROUND_HALF_EVEN,
+    ) raises -> Self:
+        """Rounds the number to the specified number of decimal places.
+
+        Args:
+            ndigits: Number of decimal places to round to.
+            rounding_mode: Rounding mode to use. Default is `ROUND_HALF_EVEN`.
+                RoundingMode.ROUND_DOWN: Round down.
+                RoundingMode.ROUND_UP: Round up.
+                RoundingMode.ROUND_HALF_UP: Round half up.
+                RoundingMode.ROUND_HALF_EVEN: Round half even.
+
+        Notes:
+            If `ndigits` is negative, the last `ndigits` digits of the integer part of
+            the number will be dropped and the scale will be `ndigits`.
+            Examples:
+                round(123.456, 2) -> 123.46
+                round(123.456, -1) -> 12E+1
+                round(123.456, -2) -> 1E+2
+                round(123.456, -3) -> 0E+3
+                round(678.890, -3) -> 1E+3
         """
         return decimojo.bigdecimal.rounding.round(self, ndigits, rounding_mode)
 

src/decimojo/bigdecimal/rounding.mojo

@@ -42,15 +42,14 @@ fn round(
             RoundingMode.ROUND_HALF_EVEN: Round half even.
 
     Notes:
-
-    If `ndigits` is negative, the last `ndigits` digits of the integer part of
-    the number will be dropped and the scale will be `ndigits`.
-    Example:
-        round(123.456, 2) -> 123.46
-        round(123.456, -1) -> 12E+1
-        round(123.456, -2) -> 1E+2
-        round(123.456, -3) -> 0E+3
-        round(678.890, -3) -> 1E+3
+        If `ndigits` is negative, the last `ndigits` digits of the integer part of
+        the number will be dropped and the scale will be `ndigits`.
+        Examples:
+            round(123.456, 2) -> 123.46
+            round(123.456, -1) -> 12E+1
+            round(123.456, -2) -> 1E+2
+            round(123.456, -3) -> 0E+3
+            round(678.890, -3) -> 1E+3
     """
     var ndigits_to_remove = number.scale - ndigits
     if ndigits_to_remove == 0:

src/decimojo/prelude.mojo

@@ -30,4 +30,11 @@ from decimojo.decimal.decimal import Decimal, Dec
 from decimojo.bigdecimal.bigdecimal import BigDecimal, BDec
 from decimojo.biguint.biguint import BigUInt, BUInt
 from decimojo.bigint.bigint import BigInt, BInt
-from decimojo.rounding_mode import RoundingMode, RM
+from decimojo.rounding_mode import (
+    RoundingMode,
+    RM,
+    ROUND_DOWN,
+    ROUND_HALF_UP,
+    ROUND_HALF_EVEN,
+    ROUND_UP,
+)

src/decimojo/rounding_mode.mojo

@@ -18,6 +18,10 @@
 """
 
 alias RM = RoundingMode
+alias ROUND_DOWN = RoundingMode.ROUND_DOWN
+alias ROUND_HALF_UP = RoundingMode.ROUND_HALF_UP
+alias ROUND_HALF_EVEN = RoundingMode.ROUND_HALF_EVEN
+alias ROUND_UP = RoundingMode.ROUND_UP
 
 
 struct RoundingMode(Stringable):

src/decimojo/tests.mojo

@@ -79,32 +79,18 @@ struct TestCase(Copyable, Movable, Stringable, Writable):
         writer.write("  description: " + self.description + "\n")
 
 
-fn load_test_cases(
-    file_path: String, table_name: String, has_expected_value: Bool = True
-) raises -> List[TestCase]:
-    """Load test cases from a TOML file for a specific table."""
-    var toml = tomlmojo.parse_file(file_path)
-    var test_cases = List[TestCase]()
-
-    # Get array of test cases
-    var cases_array = toml.get_array_of_tables(table_name)
-
-    for i in range(len(cases_array)):
-        var case_table = cases_array[i]
-        var expected_value = case_table[
-            "expected"
-        ].as_string() if has_expected_value else String("")
-        test_cases.append(
-            TestCase(
-                case_table["a"].as_string(),
-                case_table["b"].as_string(),
-                expected_value,
-                case_table["description"].as_string(),
-            )
+fn parse_file(file_path: String) raises -> tomlmojo.parser.TOMLDocument:
+    """Parse a TOML file and return the TOMLDocument."""
+    try:
+        return tomlmojo.parse_file(file_path)
+    except e:
+        raise Error(
+            "tests.parse_file(): Failed to parse TOML file:",
+            file_path,
+            "\nTraceback:",
+            e,
         )
 
-    return test_cases
-
 
 fn load_test_cases(
     toml: tomlmojo.parser.TOMLDocument, table_name: String