diff --git a/Tests/SurgeTests/ArithmeticTests.swift b/Tests/SurgeTests/ArithmeticTests.swift
index 6297b2c..f170aa4 100644
--- a/Tests/SurgeTests/ArithmeticTests.swift
+++ b/Tests/SurgeTests/ArithmeticTests.swift
@@ -27,6 +27,8 @@ import XCTest
 class ArithmeticTests: XCTestCase {
     let n = 100_000
 
+    // MARK: - Addition
+
     func test_add_array_array_float() {
         typealias Scalar = Float
 
@@ -59,6 +61,12 @@ class ArithmeticTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Addition: In Place
+
+    // FIXME: missing tests
+
+    // MARK: - Subtraction
+
     func test_sub_array_array_float() {
         typealias Scalar = Float
 
@@ -91,6 +99,12 @@ class ArithmeticTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Subtraction: In Place
+
+    // FIXME: missing tests
+
+    // MARK: - Multiplication
+
     func test_mul_array_array_float() {
         typealias Scalar = Float
 
@@ -123,6 +137,12 @@ class ArithmeticTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Multiplication: In Place
+
+    // FIXME: missing tests
+
+    // MARK: - Division
+
     func test_div_array_array_float() {
         typealias Scalar = Float
 
@@ -155,6 +175,12 @@ class ArithmeticTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Division: In Place
+
+    // FIXME: missing tests
+
+    // MARK: - Modulo
+
     func test_mod_array_array_float() {
         typealias Scalar = Float
 
@@ -187,6 +213,8 @@ class ArithmeticTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Remainder
+
     func test_remainder_array_array_float() {
         typealias Scalar = Float
 
@@ -219,6 +247,8 @@ class ArithmeticTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Square Root
+
     func test_sqrt_array_array_float() {
         typealias Scalar = Float
 
@@ -249,6 +279,8 @@ class ArithmeticTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Dot Product
+
     func test_dot_array_array_float() {
         typealias Scalar = Float
 
@@ -285,6 +317,8 @@ class ArithmeticTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Summation
+
     func test_sum() {
         let values = (0...n).map { _ in Double(arc4random()) / Double(UInt32.max) }
         var actual = 0.0
@@ -315,6 +349,8 @@ class ArithmeticTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Square Root
+
     func test_sqrt() {
         let values = (0...n).map { _ in Double(arc4random()) }
         measureAndValidateMappedFunctionWithAccuracy(source: values, member: sqrt, mapped: sqrt, accuracy: 1e-4)
@@ -325,6 +361,8 @@ class ArithmeticTests: XCTestCase {
         XCTAssertEqual(sqrt(values), [])
     }
 
+    // MARK: - Distance
+
     func test_dist_array_array_double() {
         typealias Scalar = Double
 
@@ -357,6 +395,8 @@ class ArithmeticTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-6)
     }
 
+    // MARK: - Distance Squared
+
     func test_distsq_array_array_double() {
         typealias Scalar = Double
 
diff --git a/Tests/SurgeTests/MatrixTests.swift b/Tests/SurgeTests/MatrixTests.swift
index cb944c0..150fc65 100644
--- a/Tests/SurgeTests/MatrixTests.swift
+++ b/Tests/SurgeTests/MatrixTests.swift
@@ -200,6 +200,8 @@ class MatrixTests: XCTestCase {
         XCTAssertEqual(actual_3x3, expected_3x3)
     }
 
+    // MARK: - Subscript
+
     func test_subscript_row_get() {
         typealias Scalar = Double
 
@@ -266,6 +268,8 @@ class MatrixTests: XCTestCase {
         XCTAssertEqual(matrix, expected)
     }
 
+    // MARK: - Addition
+
     func test_add_matrix_matrix_float() {
         typealias Scalar = Float
 
@@ -304,6 +308,8 @@ class MatrixTests: XCTestCase {
         XCTAssertEqual(actual, expected)
     }
 
+    // MARK: - Subtraction
+
     func test_sub_matrix_matrix_float() {
         typealias Scalar = Float
 
@@ -379,6 +385,7 @@ class MatrixTests: XCTestCase {
 
         XCTAssertEqual(actual, expected)
     }
+    // MARK: - Multiplication
 
     func test_mul_matrix_matrix_float() {
         typealias Scalar = Float
@@ -460,6 +467,8 @@ class MatrixTests: XCTestCase {
         XCTAssertEqual(actual, expected)
     }
 
+    // MARK: - Division
+
     func test_div_matrix_scalar_float() {
         typealias Scalar = Float
 
@@ -542,6 +551,8 @@ class MatrixTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Power
+
     func test_pow_matrix_scalar_float() {
         typealias Scalar = Float
 
@@ -582,6 +593,8 @@ class MatrixTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Exponential
+
     func test_exp_matrix_float() {
         typealias Scalar = Float
 
@@ -618,6 +631,8 @@ class MatrixTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Summation
+
     func test_sum_matrix_rows_double() {
         typealias Scalar = Double
 
@@ -684,6 +699,8 @@ class MatrixTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-5)
     }
 
+    // MARK: - Inverse
+
     func test_inv_matrix_double() {
         typealias Scalar = Double
 
@@ -718,6 +735,8 @@ class MatrixTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-6)
     }
 
+    // MARK: - Transpose
+
     func test_tranpose_matrix_double() {
         typealias Scalar = Double
 
@@ -754,6 +773,8 @@ class MatrixTests: XCTestCase {
         XCTAssertEqual(actual, expected)
     }
 
+    // MARK: - Determinant
+
     func test_det_matrix_double() {
         typealias Scalar = Double
 
@@ -798,6 +819,8 @@ class MatrixTests: XCTestCase {
         XCTAssertEqual(result.columns, 0)
     }
 
+    // MARK: - Eigen-Decomposition
+
     func complexVectorMatches<T: FloatingPoint>(_ a: [(T, T)], _ b: [(T, T)], accuracy: T) -> Bool {
         guard a.count == b.count else {
             return false
diff --git a/Tests/SurgeTests/VectorTests.swift b/Tests/SurgeTests/VectorTests.swift
index 951ac98..eede889 100644
--- a/Tests/SurgeTests/VectorTests.swift
+++ b/Tests/SurgeTests/VectorTests.swift
@@ -24,11 +24,15 @@ import XCTest
 // swiftlint:disable nesting type_body_length
 
 class VectorTests: XCTestCase {
+    // MARK: - Initialization
+
     func test_init() {
         let v = Vector([1.0, 2.0])
         XCTAssertEqual(v.scalars, [1.0, 2.0])
     }
 
+    // MARK: - Subscript
+
     func test_subscript() {
         typealias Scalar = Double
 
@@ -39,6 +43,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(vector[9], 10)
     }
 
+    // MARK: - Addition
+
     func test_add_vector_vector_double() {
         typealias Scalar = Double
 
@@ -97,6 +103,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Addition: In Place
+
     func test_add_in_place_vector_vector_double() {
         typealias Scalar = Double
 
@@ -175,6 +183,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Subtraction
+
     func test_sub_vector_vector_double() {
         typealias Scalar = Double
 
@@ -233,6 +243,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Subtraction: In Place
+
     func test_sub_in_place_vector_vector_double() {
         typealias Scalar = Double
 
@@ -340,6 +352,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Multiplication
+
     func test_mul_vector_scalar_double() {
         typealias Scalar = Double
 
@@ -410,6 +424,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected)
     }
 
+    // MARK: - Multiplication: In Place
+
     func test_mul_in_place_vector_scalar_double() {
         typealias Scalar = Double
 
@@ -450,6 +466,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Division
+
     func test_div_vector_scalar_double() {
         typealias Scalar = Double
 
@@ -480,6 +498,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-5)
     }
 
+    // MARK: - Division: In Place
+
     func test_div_in_place_vector_scalar_double() {
         typealias Scalar = Double
 
@@ -520,6 +540,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-5)
     }
 
+    // MARK: - Element-wise Multiplication
+
     func test_elmul_double() {
         typealias Scalar = Double
 
@@ -548,6 +570,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Element-wise Multiplication: In Place
+
     func test_elmul_in_place_double() {
         typealias Scalar = Double
 
@@ -586,6 +610,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-8)
     }
 
+    // MARK: - Element-wise Division
+
     func test_eldiv_double() {
         typealias Scalar = Double
 
@@ -614,6 +640,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-6)
     }
 
+    // MARK: - Element-wise Division: In Place
+
     func test_eldiv_in_place_double() {
         typealias Scalar = Double
 
@@ -652,6 +680,12 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-6)
     }
 
+    // MARK: - Dot Product
+
+    // FIXME: missing tests
+
+    // MARK: - Power
+
     func test_pow_vector_scalar_double() {
         typealias Scalar = Double
 
@@ -680,6 +714,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-5)
     }
 
+    // MARK: - Exponential
+
     func test_exp_vector_double() {
         typealias Scalar = Double
 
@@ -714,6 +750,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-2)
     }
 
+    // MARK: - Distance
+
     func test_dist_vector_vector_double() {
         typealias Scalar = Double
 
@@ -744,6 +782,8 @@ class VectorTests: XCTestCase {
         XCTAssertEqual(actual, expected, accuracy: 1e-6)
     }
 
+    // MARK: - Distance Squared
+
     func test_distsq_vector_vector_double() {
         typealias Scalar = Double