Add data handling and test isolation guidance

- add SCM guidance for deriving base quantities through line unit-of-measure validation`n- add security guidance for parameterizing SetFilter with external text`n- add test isolation guidance for resetting per-test state before initialization guards`n- add web-service guidance for JSON null handling and invariant standard format 9`n- route and cover all five rules with paired evaluation fixtures

microsoft/knowledge/testing/reset-per-test-state-before-the-isinitialized-guard.bad.al

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+codeunit 50411 "Test Sales Setup Initialize Bad"
+{
+    Subtype = Test;
+
+    [Test]
+    [HandlerFunctions('CustomerCardHandler')]
+    procedure CustomerCardOpensForSelectedCustomer()
+    var
+        Customer: Record Customer;
+    begin
+        Initialize();
+        LibrarySales.CreateCustomer(Customer);
+        LibraryVariableStorage.Enqueue(Customer."No.");
+
+        Page.RunModal(Page::"Customer Card", Customer);
+
+        LibraryVariableStorage.AssertEmpty();
+    end;
+
+    [Test]
+    procedure StockoutWarningCanBeDisabled()
+    var
+        SalesSetup: Record "Sales & Receivables Setup";
+    begin
+        Initialize();
+
+        LibrarySales.SetStockoutWarning(false);
+
+        SalesSetup.Get();
+        Assert.IsFalse(SalesSetup."Stockout Warning", 'The stockout warning was not disabled.');
+    end;
+
+    local procedure Initialize()
+    begin
+        if IsInitialized then
+            exit;
+
+        LibraryVariableStorage.Clear();
+        LibrarySetupStorage.Restore();
+        LibrarySales.SetStockoutWarning(true);
+        IsInitialized := true;
+        LibrarySetupStorage.SaveSalesSetup();
+    end;
+
+    [ModalPageHandler]
+    procedure CustomerCardHandler(var CustomerCard: TestPage "Customer Card")
+    begin
+        Assert.AreEqual(LibraryVariableStorage.DequeueText(), CustomerCard."No.".Value(), 'The customer card opened for the wrong customer.');
+    end;
+
+    var
+        Assert: Codeunit Assert;
+        LibrarySales: Codeunit "Library - Sales";
+        LibrarySetupStorage: Codeunit "Library - Setup Storage";
+        LibraryVariableStorage: Codeunit "Library - Variable Storage";
+        IsInitialized: Boolean;
+}

microsoft/knowledge/testing/reset-per-test-state-before-the-isinitialized-guard.good.al

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+codeunit 50410 "Test Sales Setup Initialize Good"
+{
+    Subtype = Test;
+
+    [Test]
+    [HandlerFunctions('CustomerCardHandler')]
+    procedure CustomerCardOpensForSelectedCustomer()
+    var
+        Customer: Record Customer;
+    begin
+        Initialize();
+        LibrarySales.CreateCustomer(Customer);
+        LibraryVariableStorage.Enqueue(Customer."No.");
+
+        Page.RunModal(Page::"Customer Card", Customer);
+
+        LibraryVariableStorage.AssertEmpty();
+    end;
+
+    [Test]
+    procedure StockoutWarningCanBeDisabled()
+    var
+        SalesSetup: Record "Sales & Receivables Setup";
+    begin
+        Initialize();
+
+        LibrarySales.SetStockoutWarning(false);
+
+        SalesSetup.Get();
+        Assert.IsFalse(SalesSetup."Stockout Warning", 'The stockout warning was not disabled.');
+    end;
+
+    local procedure Initialize()
+    begin
+        LibraryTestInitialize.OnTestInitialize(Codeunit::"Test Sales Setup Initialize Good");
+        LibraryVariableStorage.Clear();
+        LibrarySetupStorage.Restore();
+
+        if IsInitialized then
+            exit;
+        LibraryTestInitialize.OnBeforeTestSuiteInitialize(Codeunit::"Test Sales Setup Initialize Good");
+
+        LibrarySales.SetStockoutWarning(true);
+        IsInitialized := true;
+        LibrarySetupStorage.SaveSalesSetup();
+        LibraryTestInitialize.OnAfterTestSuiteInitialize(Codeunit::"Test Sales Setup Initialize Good");
+    end;
+
+    [ModalPageHandler]
+    procedure CustomerCardHandler(var CustomerCard: TestPage "Customer Card")
+    begin
+        Assert.AreEqual(LibraryVariableStorage.DequeueText(), CustomerCard."No.".Value(), 'The customer card opened for the wrong customer.');
+    end;
+
+    var
+        Assert: Codeunit Assert;
+        LibrarySales: Codeunit "Library - Sales";
+        LibrarySetupStorage: Codeunit "Library - Setup Storage";
+        LibraryTestInitialize: Codeunit "Library - Test Initialize";
+        LibraryVariableStorage: Codeunit "Library - Variable Storage";
+        IsInitialized: Boolean;
+}

microsoft/knowledge/testing/reset-per-test-state-before-the-isinitialized-guard.md

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+---
+bc-version: [all]
+domain: testing
+keywords: [initialize, isinitialized, library-test-initialize, ontestinitialize, library-variable-storage, library-setup-storage, test-fixture, test-codeunit]
+technologies: [al]
+countries: [w1]
+application-area: [all]
+---
+
+# Reset per-test state before the IsInitialized guard
+
+## Description
+
+Standard Business Central test codeunits call a local `Initialize` procedure at the start of every test method. Global variables in a test codeunit keep their values between the codeunit's test methods, so a Boolean such as `IsInitialized` lets `Initialize` run expensive shared setup only once. The procedure therefore has two parts with different lifetimes: work that must run before **every** test, and one-time setup behind the guard. If per-test reset is placed after the guard, it runs only for the first test. Values left in `Library - Variable Storage` by a failed test, or setup records a test changed, then leak into later tests, which pass or fail depending on execution order.
+
+## Best Practice
+
+Call `Initialize()` as the first statement of every test method. Inside it, keep this order, which the Base Application tests follow:
+
+1. Per-test work, before the guard: raise `"Library - Test Initialize".OnTestInitialize`, call `LibraryVariableStorage.Clear()`, and call `LibrarySetupStorage.Restore()` when setup tables were saved.
+2. `if IsInitialized then exit;`
+3. One-time work: raise `OnBeforeTestSuiteInitialize`, create the shared fixture and setup values, set `IsInitialized := true`, save the setup tables that tests may change (for example `LibrarySetupStorage.SaveSalesSetup()`), and raise `OnAfterTestSuiteInitialize`.
+
+Create data that a single test changes inside that test, not in the shared fixture. Base Application suites also commit after the one-time setup so the shared fixture survives each test's transaction; whether that commit is valid depends on the test transaction model and runner isolation, see [`transactionmodel-attribute-governs-test-transactions.md`](transactionmodel-attribute-governs-test-transactions.md) and [`testisolation-belongs-on-the-test-runner.md`](testisolation-belongs-on-the-test-runner.md).
+
+A test codeunit with no shared setup and no queued values doesn't need an `Initialize` procedure. Don't report its absence on its own.
+
+See sample: [`reset-per-test-state-before-the-isinitialized-guard.good.al`](reset-per-test-state-before-the-isinitialized-guard.good.al).
+
+## Anti Pattern
+
+`if IsInitialized then exit;` as the first statement of `Initialize`, followed by `LibraryVariableStorage.Clear()`, `LibrarySetupStorage.Restore()`, or other reset calls that are then skipped for every test after the first. A related defect is a test method in a codeunit that uses the pattern but doesn't call `Initialize()`, so it runs with whatever state the previous test left. Detection signal: in a `Subtype = Test` codeunit, a reset call placed after the `IsInitialized` exit, or a `[Test]` procedure that uses shared globals or queued values without first calling `Initialize()`.
+
+See sample: [`reset-per-test-state-before-the-isinitialized-guard.bad.al`](reset-per-test-state-before-the-isinitialized-guard.bad.al).
+
+## References
+
+- [BCApps: `Initialize` in the ERM Sales Document tests](https://github.com/microsoft/BCApps/blob/4abbb8ff848cdcb4e1187fc7a3e2da0612dd0d2b/src/Layers/W1/Tests/ERM-Sales/ERMSalesDocument.Codeunit.al)
+- [BCApps: Library - Test Initialize events](https://github.com/microsoft/BCApps/blob/4abbb8ff848cdcb4e1187fc7a3e2da0612dd0d2b/src/Layers/W1/Tests/ApplicationTestLibrary/LibraryTestInitialize.Codeunit.al)
+- [BCApps: Library - Setup Storage](https://github.com/microsoft/BCApps/blob/4abbb8ff848cdcb4e1187fc7a3e2da0612dd0d2b/src/Layers/W1/Tests/ApplicationTestLibrary/LibrarySetupStorage.Codeunit.al)
+- [Testing the application](https://learn.microsoft.com/en-us/dynamics365/business-central/dev-itpro/developer/devenv-testing-application)