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100 lines
3.7 KiB
Markdown
100 lines
3.7 KiB
Markdown
---
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bc-version: [all]
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domain: testing
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keywords: [test, when, scenario, single-action, bdd, atdd, given-when-then]
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technologies: [al]
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countries: [w1]
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application-area: [all]
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---
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## Description
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Each test procedure must contain exactly **one** `[WHEN]` block — one action that
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triggers the behaviour under test. A test with multiple WHENs ("do A, then do B,
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then check C") is really two or more tests in disguise. Split them.
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This constraint serves two purposes:
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1. **Failure isolation** — when the test fails you know which action caused it.
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2. **Readable specification** — each test reads as a single, falsifiable claim
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about the system's behaviour.
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A scenario that genuinely requires a precondition action (e.g. "post an order so
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that a ledger entry exists") belongs in `[GIVEN]`. Only the action being asserted
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belongs in `[WHEN]`.
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## Anti Pattern
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// WRONG: two actions in one test
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[Test]
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procedure GetPrice_ThenGetDiscount_ReturnsCorrectValues()
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var
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UnitPrice, LineDiscPct: Decimal;
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begin
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// [GIVEN] ...
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// [WHEN] first action
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FindPriceMgt.GetSalesPrice(CustomerNo, ItemNo, '', UnitPrice, LineDiscPct);
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// [WHEN] second action — this is a second test in disguise
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FindPriceMgt.GetSalesPriceTiers(CustomerNo, ItemNo, '', TempBuffer);
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// [THEN] asserting two unrelated things
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Assert.AreEqual(100, UnitPrice, '');
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Assert.IsFalse(TempBuffer.IsEmpty(), '');
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end;
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## Best Practice
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// CORRECT: split into two focused tests
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[Test]
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procedure GetPrice_CustomerPrice_ReturnsCorrectUnitPrice()
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var
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UnitPrice, LineDiscPct: Decimal;
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begin
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// [GIVEN] a customer with a price list line at 100
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WarecoLib.GivenCustomerWithPrice(Customer, Item, '', 100);
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// [WHEN]
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FindPriceMgt.GetSalesPrice(Customer."No.", Item."No.", '', UnitPrice, LineDiscPct);
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// [THEN]
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Assert.AreEqual(100, UnitPrice, 'Unit price must match price list');
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end;
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[Test]
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procedure GetPriceTiers_CustomerTier_ReturnsOneTierLine()
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var
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TempBuffer: Record "Find Price Tier Buffer" temporary;
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begin
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// [GIVEN] a customer with a tier price at min qty 10
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WarecoLib.GivenCustomerWithTierPrice(Customer, Item, '', 10, 90);
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// [WHEN]
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FindPriceMgt.GetSalesPriceTiers(Customer."No.", Item."No.", '', TempBuffer);
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// [THEN]
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Assert.AreEqual(1, TempBuffer.Count(), 'Exactly one tier line expected');
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end;
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## Flow tests — the deliberate exception
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A **flow test** verifies the accumulated outcome of a multi-round business
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flow (partial receipt then invoicing, multiple posting rounds against one
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document). The sequence IS the scenario — splitting it loses the interaction
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under test. Multiple `[WHEN]` blocks are permitted when ALL of these hold:
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1. The name declares the flow (`SVPartialFlowTests`,
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`ReceiveThenInvoice_QuantitiesAreCorrect`).
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2. Each `[WHEN]` is labelled as a round of ONE scenario ("Runde 1: kun
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modtagelse"), not as an unrelated action.
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3. The `[THEN]` asserts the accumulated end-state. If the assertions
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decompose cleanly per action, it is two tests in disguise: split.
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Unit-level tests keep the strict one-WHEN rule without exception. (Edison
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eval 2026-07-02, Jernpladsen @ b7656b1: five deliberate round-labelled flow
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procedures in SVPartialFlowTests — the rule previously gave no verdict.)
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## Naming implication
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The procedure name should make the single WHEN self-evident.
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A name with "And" or "Then" in the middle is a strong signal to split:
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- `GetPrice_AndDiscount_ReturnsValues` → split
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- `GetPrice_CustomerPrice_ReturnsUnitPrice` → good
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- `ReceiveThenInvoice_QuantitiesAreCorrect` → legitimate flow test IF the
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flow-test conditions above are met
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