precision to steel decimal crate implemented

steel_decimal/tests/function_tests.rs

@@ -243,3 +243,55 @@ fn test_scientific_notation(#[case] a: &str, #[case] b: &str, #[case] expected:
     let result = decimal_add(a.to_string(), b.to_string()).unwrap();
     assert_eq!(result, expected);
 }
+
+// Test precision behavior
+#[rstest]
+#[case("5", "0", "5")]           // Integer + integer = integer
+#[case("5.0", "0", "5.0")]       // Decimal + integer = decimal
+#[case("5.00", "0.00", "5.00")]  // Preserves highest precision
+#[case("5.1", "0.23", "5.33")]   // Normal decimal arithmetic
+fn test_precision_preservation(#[case] a: &str, #[case] b: &str, #[case] expected: &str) {
+    let result = decimal_add(a.to_string(), b.to_string()).unwrap();
+    assert_eq!(result, expected);
+}
+
+// Test explicit precision functions
+#[rstest]
+#[case("5.123", "2.456", 0, "8")]     // 0 decimal places
+#[case("5.123", "2.456", 2, "7.58")]  // 2 decimal places
+#[case("5.123", "2.456", 4, "7.5790")] // 4 decimal places
+fn test_explicit_precision(#[case] a: &str, #[case] b: &str, #[case] precision: u32, #[case] expected: &str) {
+    let result = decimal_add_p(a.to_string(), b.to_string(), precision).unwrap();
+    assert_eq!(result, expected);
+}
+
+// Test scientific notation edge cases
+#[rstest]
+#[case("1e0", "1")]       // Simple case
+#[case("1.0e0", "1.0")]   // Preserves decimal
+#[case("1e-2", "0.01")]   // Negative exponent
+#[case("1.5e-3", "0.0015")] // Decimal + negative exponent
+#[case("2.5e2", "250.0")] // Decimal + positive exponent
+fn test_scientific_edge_cases(#[case] input: &str, #[case] expected: &str) {
+    let result = to_decimal(input.to_string()).unwrap();
+    assert_eq!(result, expected);
+}
+
+// Test precision functions
+#[test]
+fn test_precision_functions() {
+    // Test setting precision
+    assert_eq!(set_precision(2), "Precision set to 2 decimal places");
+    assert_eq!(get_precision(), "2");
+
+    // Test with precision set
+    let result = decimal_add("1.567".to_string(), "2.891".to_string()).unwrap();
+    assert_eq!(result, "4.46");
+
+    // Test clearing precision
+    assert_eq!(get_precision(), "full");
+
+    // Test with full precision
+    let result = decimal_add("1.567".to_string(), "2.891".to_string()).unwrap();
+    assert_eq!(result, "4.458");
+}