diff --git a/Package.swift b/Package.swift
index da0b2ea6..50fa8597 100644
--- a/Package.swift
+++ b/Package.swift
@@ -4,62 +4,109 @@
 import PackageDescription
 
 let package = Package(
-    name: "SnapshotPreviews",
-    platforms: [.iOS(.v15), .macOS(.v12), .watchOS(.v9)],
-    products: [
-        // Products define the executables and libraries a package produces, making them visible to other packages.
-        .library(
-          name: "PreviewGallery",
-          type: .static, // Replace this to build dynamic
-          targets: ["PreviewGallery"]),
-        // Test library to import in your XCTest target.
-        // This is the only library that depends on XCTest.framework
-        .library(
-          name: "SnapshottingTests",
-          type: .static, // Replace this to build dynamic
-          targets: ["SnapshottingTests"]),
-        // Link the main app to this target to use custom snapshot settings
-        // This lib does not get inserted when running tests to avoid
-        // duplicate symbols.
-        .library(
-          name: "SnapshotPreferences",
-          targets: ["SnapshotPreferences"]),
-        // Core functionality for snapshotting exported from the internal package
-        .library(
-          name: "SnapshotPreviewsCore",
-          targets: ["SnapshotPreviewsCore"]),
-        // Dynamic library that your main app will have inserted to generate previews
-        .library(
-          name: "Snapshotting",
-          type: .dynamic,
-          targets: ["Snapshotting"]),
-    ],
-    dependencies: [
-      .package(url: "https://github.com/swhitty/FlyingFox.git", exact: "0.16.0"),
-      .package(url: "https://github.com/EmergeTools/AccessibilitySnapshot.git", exact: "1.0.2"),
-      .package(url: "https://github.com/EmergeTools/SimpleDebugger.git", exact: "1.0.0"),
-    ],
-    targets: [
-        // Targets are the basic building blocks of a package, defining a module or a test suite.
-        // Targets can depend on other targets in this package and products from dependencies.
-        // Target that provides the XCTest
-      .target(name: "SnapshottingTestsObjc", dependencies: [.product(name: "SimpleDebugger", package: "SimpleDebugger", condition: .when(platforms: [.iOS, .macOS, .macCatalyst]))]),
-        .target(name: "SnapshottingTests", dependencies: ["SnapshotPreviewsCore", "SnapshottingTestsObjc"]),
-        .target(name: "SnapshotSharedModels"),
-        // Core functionality
-        .target(name: "SnapshotPreviewsCore", dependencies: ["PreviewsSupport", "SnapshotSharedModels", .product(name: "AccessibilitySnapshotCore", package: "AccessibilitySnapshot", condition: .when(platforms: [.iOS, .macCatalyst]))]),
-        .target(name: "SnapshotPreferences", dependencies: ["SnapshotSharedModels"]),
-        // Inserted dylib
-        .target(name: "Snapshotting", dependencies: ["SnapshottingSwift"]),
-        // Swift code in the inserted dylib
-        .target(name: "SnapshottingSwift", dependencies: ["SnapshotPreviewsCore", .product(name: "FlyingFox", package: "FlyingFox")]),
-        .target(name: "PreviewGallery", dependencies: ["SnapshotPreviewsCore", "SnapshotPreferences"]),
-        .binaryTarget(
-          name: "PreviewsSupport",
-          path: "PreviewsSupport/PreviewsSupport.xcframework"),
-        .testTarget(
-            name: "SnapshotPreviewsTests",
-            dependencies: ["SnapshotPreviewsCore"]),
-    ],
-    cxxLanguageStandard: .cxx11
+  name: "SnapshotPreviews",
+  platforms: [.iOS(.v15), .macOS(.v12), .watchOS(.v9)],
+  products: [
+    // Products define the executables and libraries a package produces, making them visible to other packages.
+    .library(
+      name: "PreviewGallery",
+      type: .static,  // Replace this to build dynamic
+      targets: ["PreviewGallery"]
+    ),
+    // Test library to import in your XCTest target.
+    // This is the only library that depends on XCTest.framework
+    .library(
+      name: "SnapshottingTests",
+      type: .static,  // Replace this to build dynamic
+      targets: ["SnapshottingTests"]
+    ),
+    // Link the main app to this target to use custom snapshot settings
+    // This lib does not get inserted when running tests to avoid
+    // duplicate symbols.
+    .library(
+      name: "SnapshotPreferences",
+      targets: ["SnapshotPreferences"]
+    ),
+    // Core functionality for snapshotting exported from the internal package
+    .library(
+      name: "SnapshotPreviewsCore",
+      targets: ["SnapshotPreviewsCore"]
+    ),
+    // Dynamic library that your main app will have inserted to generate previews
+    .library(
+      name: "Snapshotting",
+      type: .dynamic,
+      targets: ["Snapshotting"]
+    ),
+  ],
+  dependencies: [
+    .package(url: "https://github.com/swhitty/FlyingFox.git", exact: "0.16.0"),
+    .package(
+      url: "https://github.com/EmergeTools/AccessibilitySnapshot.git",
+      exact: "1.0.2"
+    ),
+    .package(
+      url: "https://github.com/EmergeTools/SimpleDebugger.git",
+      exact: "1.0.0"
+    ),
+  ],
+  targets: [
+    // Targets are the basic building blocks of a package, defining a module or a test suite.
+    // Targets can depend on other targets in this package and products from dependencies.
+    // Target that provides the XCTest
+    .target(
+      name: "SnapshottingTestsObjc",
+      dependencies: [
+        .product(
+          name: "SimpleDebugger",
+          package: "SimpleDebugger",
+          condition: .when(platforms: [.iOS, .macOS, .macCatalyst])
+        )
+      ]
+    ),
+    .target(
+      name: "SnapshottingTests",
+      dependencies: ["SnapshotPreviewsCore", "SnapshottingTestsObjc"]
+    ),
+    .target(name: "SnapshotSharedModels"),
+    // Core functionality
+    .target(
+      name: "SnapshotPreviewsCore",
+      dependencies: [
+        "PreviewsSupport", "SnapshotSharedModels",
+        .product(
+          name: "AccessibilitySnapshotCore",
+          package: "AccessibilitySnapshot",
+          condition: .when(platforms: [.iOS, .macCatalyst])
+        ),
+      ]
+    ),
+    .target(
+      name: "SnapshotPreferences",
+      dependencies: ["SnapshotSharedModels"]
+    ),
+    // Inserted dylib
+    .target(name: "Snapshotting", dependencies: ["SnapshottingSwift"]),
+    // Swift code in the inserted dylib
+    .target(
+      name: "SnapshottingSwift",
+      dependencies: [
+        "SnapshotPreviewsCore",
+        .product(name: "FlyingFox", package: "FlyingFox"),
+      ]
+    ),
+    .target(
+      name: "PreviewGallery",
+      dependencies: ["SnapshotPreviewsCore", "SnapshotPreferences"]
+    ),
+    .binaryTarget(
+      name: "PreviewsSupport",
+      path: "PreviewsSupport/PreviewsSupport.xcframework"
+    ),
+    .testTarget(
+      name: "SnapshotPreviewsTests",
+      dependencies: ["SnapshotPreviewsCore", "SnapshotPreferences"]
+    ),
+  ],
+  cxxLanguageStandard: .cxx11
 )
diff --git a/Sources/SnapshotPreviewsCore/EmergeModifierView.swift b/Sources/SnapshotPreviewsCore/EmergeModifierView.swift
new file mode 100644
index 00000000..a468a6da
--- /dev/null
+++ b/Sources/SnapshotPreviewsCore/EmergeModifierView.swift
@@ -0,0 +1,64 @@
+//
+//  ModifierFinder.swift
+//
+//
+//  Created by Noah Martin on 7/8/24.
+//
+
+import Foundation
+import SnapshotSharedModels
+import SwiftUI
+
+public struct EmergeModifierView: View {
+
+  private static let modifierFinderClass =
+    (NSClassFromString("EmergeModifierFinder") as? NSObject.Type)?.init()
+  private static let finder =
+    modifierFinderClass != nil
+    ? Mirror(reflecting: modifierFinderClass!).descendant("finder")
+      as? (any View) -> any View : nil
+  private static let modifierState =
+    NSClassFromString("EmergeModifierState") as? NSObject.Type
+  private static let stateMirror =
+    modifierState != nil
+    ? Mirror(
+      reflecting: modifierState!
+        .perform(NSSelectorFromString("shared"))
+        .takeUnretainedValue()
+    ) : nil
+
+  private let internalView: AnyView
+
+  init(wrapped: some View) {
+    let rootView = Self.finder?(wrapped)
+    internalView = rootView != nil ? AnyView(rootView!) : AnyView(wrapped)
+  }
+
+  public var body: some View {
+    internalView
+  }
+
+  var emergeRenderingMode: EmergeRenderingMode? {
+    let renderingMode =
+      Self.stateMirror?.descendant("renderingMode")
+      as? EmergeRenderingMode.RawValue
+    return renderingMode != nil
+      ? EmergeRenderingMode(rawValue: renderingMode!) : nil
+  }
+
+  var accessibilityEnabled: Bool? {
+    Self.stateMirror?.descendant("accessibilityEnabled") as? Bool
+  }
+
+  var appStoreSnapshot: Bool? {
+    Self.stateMirror?.descendant("appStoreSnapshot") as? Bool
+  }
+
+  var precision: Float? {
+    Self.stateMirror?.descendant("precision") as? Float
+  }
+
+  var supportsExpansion: Bool {
+    Self.stateMirror?.descendant("expansionPreference") as? Bool ?? true
+  }
+}
diff --git a/Sources/SnapshotPreviewsCore/ModifierFinder.swift b/Sources/SnapshotPreviewsCore/ModifierFinder.swift
deleted file mode 100644
index 476aada7..00000000
--- a/Sources/SnapshotPreviewsCore/ModifierFinder.swift
+++ /dev/null
@@ -1,53 +0,0 @@
-//
-//  ModifierFinder.swift
-//
-//
-//  Created by Noah Martin on 7/8/24.
-//
-
-import Foundation
-import SwiftUI
-import SnapshotSharedModels
-
-private let modifierFinderClass = (NSClassFromString("EmergeModifierFinder") as? NSObject.Type)?.init()
-private let finder = modifierFinderClass != nil ? Mirror(reflecting: modifierFinderClass!).descendant("finder") as? (any View) -> any View : nil
-private let modifierState = NSClassFromString("EmergeModifierState") as? NSObject.Type
-private let stateMirror = modifierState != nil ? Mirror(
-  reflecting: modifierState!
-    .perform(NSSelectorFromString("shared"))
-    .takeUnretainedValue()) : nil
-
-public struct EmergeModifierView: View {
-
-  private let internalView: AnyView
-
-  init(wrapped: some View) {
-    let rootView = finder?(wrapped)
-    internalView = rootView != nil ? AnyView(rootView!) : AnyView(wrapped)
-  }
-
-  public var body: some View {
-    internalView
-  }
-
-  var emergeRenderingMode: EmergeRenderingMode? {
-    let renderingMode = stateMirror?.descendant("renderingMode") as? EmergeRenderingMode.RawValue
-    return renderingMode != nil ? EmergeRenderingMode(rawValue: renderingMode!) : nil
-  }
-
-  var accessibilityEnabled: Bool? {
-    stateMirror?.descendant("accessibilityEnabled") as? Bool
-  }
-
-  var appStoreSnapshot: Bool? {
-    stateMirror?.descendant("appStoreSnapshot") as? Bool
-  }
-
-  var precision: Float? {
-    stateMirror?.descendant("precision") as? Float
-  }
-
-  var supportsExpansion: Bool {
-    stateMirror?.descendant("expansionPreference") as? Bool ?? true
-  }
-}
diff --git a/Tests/SnapshotPreviewsTests/ConformanceLookupTests.swift b/Tests/SnapshotPreviewsTests/ConformanceLookupTests.swift
new file mode 100644
index 00000000..fd93d689
--- /dev/null
+++ b/Tests/SnapshotPreviewsTests/ConformanceLookupTests.swift
@@ -0,0 +1,17 @@
+import XCTest
+
+@testable import SnapshotPreviewsCore
+
+final class ConformanceLookupTests: XCTestCase {
+  func test_getPreviewTypes() throws {
+    let types = getPreviewTypes()
+    XCTAssertEqual(types.count, 1)
+
+    let firstType = types.first!
+    XCTAssertEqual(
+      "SnapshotPreviewsTests.$s21SnapshotPreviewsTests0019TestViewswift_DJEEdfMX15_0_33_B5E96601318DE1EC85533DD88EB53190Ll7PreviewfMf_15PreviewRegistryfMu_",
+      firstType.name
+    )
+    XCTAssertEqual("PreviewRegistry", firstType.proto)
+  }
+}
diff --git a/Tests/SnapshotPreviewsTests/ETBrowserTests.swift b/Tests/SnapshotPreviewsTests/ETBrowserTests.swift
deleted file mode 100644
index e815f157..00000000
--- a/Tests/SnapshotPreviewsTests/ETBrowserTests.swift
+++ /dev/null
@@ -1,12 +0,0 @@
-import XCTest
-@testable import SnapshotPreviewsCore
-
-final class SnapshotPreviewsTest: XCTestCase {
-    func testExample() throws {
-        // XCTest Documentation
-        // https://developer.apple.com/documentation/xctest
-
-        // Defining Test Cases and Test Methods
-        // https://developer.apple.com/documentation/xctest/defining_test_cases_and_test_methods
-    }
-}
diff --git a/Tests/SnapshotPreviewsTests/EmergeModifierStateTests.swift b/Tests/SnapshotPreviewsTests/EmergeModifierStateTests.swift
new file mode 100644
index 00000000..e6e5b6e5
--- /dev/null
+++ b/Tests/SnapshotPreviewsTests/EmergeModifierStateTests.swift
@@ -0,0 +1,72 @@
+//
+//  EmergeModifierViewTests.swift
+//  SnapshotPreviews
+//
+//  Created by Trevor Elkins on 4/30/25.
+//
+
+import SwiftUI
+import XCTest
+
+@testable import SnapshotPreferences
+@testable import SnapshotSharedModels
+@testable import SnapshotPreviewsCore
+
+final class EmergeModifierStateTests: XCTestCase {
+
+  override func setUp() {
+    super.setUp()
+    EmergeModifierState.shared.reset()
+  }
+
+  func test_storesRenderingMode() {
+    let view = makeBaseText().emergeRenderingMode(.uiView)
+    let state = state(for: view)
+    XCTAssertEqual(state.renderingMode, EmergeRenderingMode.uiView.rawValue)
+  }
+
+  func test_storesPrecision() throws {
+    let view = makeBaseText().emergeSnapshotPrecision(0.95)
+    let state = state(for: view)
+    let precision = try XCTUnwrap(state.precision)
+    XCTAssertEqual(precision, 0.95, accuracy: .ulpOfOne)
+  }
+
+  func test_storesExpansionPreference() {
+    let view = makeBaseText().emergeExpansion(false)
+    let state = state(for: view)
+    XCTAssertEqual(state.expansionPreference, false)
+  }
+
+  func test_storesAccessibilityFlag() {
+    let view = makeBaseText().emergeAccessibility(true)
+    let state = state(for: view)
+    XCTAssertEqual(state.accessibilityEnabled, true)
+  }
+
+  func test_storesAppStoreSnapshotFlag() {
+    let view = makeBaseText().emergeAppStoreSnapshot(true)
+    let state = state(for: view)
+    XCTAssertEqual(state.appStoreSnapshot, true)
+  }
+
+  private func makeBaseText() -> Text { Text("Hello") }
+
+  private func state(
+    for view: some View,
+    file: StaticString = #file,
+    line: UInt = #line
+  ) -> EmergeModifierState {
+    let wrapped = EmergeModifierView(wrapped: view)
+    let hosting = UIHostingController(rootView: wrapped)
+
+    let window = UIWindow(frame: UIScreen.main.bounds)
+    window.rootViewController = hosting
+    window.makeKeyAndVisible()
+
+    // Give SwiftUI one tick to propagate preferences
+    RunLoop.main.run(until: Date(timeIntervalSinceNow: 0.01))
+
+    return EmergeModifierState.shared
+  }
+}
diff --git a/Tests/SnapshotPreviewsTests/ScrollExpansionTests.swift b/Tests/SnapshotPreviewsTests/ScrollExpansionTests.swift
new file mode 100644
index 00000000..68167a6c
--- /dev/null
+++ b/Tests/SnapshotPreviewsTests/ScrollExpansionTests.swift
@@ -0,0 +1,111 @@
+//
+//  ScrollExpansionTests.swift
+//  SnapshotPreviews
+//
+//  Created by Trevor Elkins on 5/1/25.
+//
+
+import UIKit
+import XCTest
+
+@testable import SnapshotPreviewsCore
+
+final class ScrollExpansionUIKitTests: XCTestCase {
+  func test_expandsWhenNeeded() {
+    let vc = makeVC(visible: 300, content: 500)
+
+    vc.updateHeight {}
+
+    XCTAssertEqual(
+      vc.heightAnchor?.constant,
+      500,
+      "Height should increase by diff between content & visible"
+    )
+    XCTAssertEqual(
+      vc.previousHeight,
+      300,
+      "previousHeight must capture last visible height"
+    )
+  }
+
+  func test_doesNotExpandWhenNotSupported() {
+    let vc = makeVC(visible: 300, content: 500, supportsExpansion: false)
+
+    vc.updateHeight {}
+
+    XCTAssertEqual(
+      vc.heightAnchor?.constant,
+      300,
+      "Constraint must stay unchanged when expansion is off"
+    )
+    XCTAssertNil(
+      vc.previousHeight,
+      "previousHeight should remain nil when no expansion happens"
+    )
+  }
+
+  func test_doesNotExpandAgainIfAlreadyExpanded() {
+    let vc = makeVC(visible: 300, content: 500)
+
+    vc.updateHeight {}
+    vc.updateHeight {}  // second call — should be a no-op
+
+    XCTAssertEqual(
+      vc.heightAnchor?.constant,
+      500,
+      "Second invocation must not change the constant"
+    )
+  }
+
+  private func makeVC(
+    visible: CGFloat,
+    content: CGFloat,
+    supportsExpansion: Bool = true
+  ) -> ExpandableVC {
+    let vc = ExpandableVC(
+      visible: visible,
+      content: content,
+      initialConstant: visible
+    )
+    vc.supportsExpansion = supportsExpansion
+    return vc
+  }
+}
+
+private final class ExpandableVC: UIViewController, ScrollExpansionProviding {
+
+  var previousHeight: CGFloat?
+  var supportsExpansion: Bool = true
+
+  private(set) var heightConstraint: NSLayoutConstraint?
+  var heightAnchor: NSLayoutConstraint? { heightConstraint }
+
+  init(
+    visible: CGFloat,
+    content: CGFloat,
+    initialConstant: CGFloat? = 100
+  ) {
+    super.init(nibName: nil, bundle: nil)
+
+    let scroll = UIScrollView()
+    scroll.contentSize = CGSize(width: 320, height: content)
+    scroll.frame = CGRect(x: 0, y: 0, width: 320, height: visible)
+    scroll.translatesAutoresizingMaskIntoConstraints = false
+    view.addSubview(scroll)
+    NSLayoutConstraint.activate([
+      scroll.topAnchor.constraint(equalTo: view.topAnchor),
+      scroll.bottomAnchor.constraint(equalTo: view.bottomAnchor),
+      scroll.leadingAnchor.constraint(equalTo: view.leadingAnchor),
+      scroll.trailingAnchor.constraint(equalTo: view.trailingAnchor),
+    ])
+
+    if let constant = initialConstant {
+      heightConstraint = view.heightAnchor.constraint(equalToConstant: constant)
+      heightConstraint?.isActive = true
+    }
+  }
+
+  required init?(coder: NSCoder) {
+    fatalError("init(coder:) has not been implemented")
+  }
+}
diff --git a/Tests/SnapshotPreviewsTests/TestView.swift b/Tests/SnapshotPreviewsTests/TestView.swift
new file mode 100644
index 00000000..461d04f0
--- /dev/null
+++ b/Tests/SnapshotPreviewsTests/TestView.swift
@@ -0,0 +1,18 @@
+//
+//  TestView.swift
+//  SnapshotPreviews
+//
+//  Created by Trevor Elkins on 4/30/25.
+//
+
+import SwiftUI
+
+struct TestView: View {
+  var body: some View {
+    Text("Hello world!")
+  }
+}
+
+#Preview {
+  TestView()
+}