> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ton.org/llms.txt
> Use this file to discover all available pages before exploring further.

<AgentInstructions>

## Submitting Feedback

If you encounter incorrect, outdated, or confusing documentation on this page, submit feedback:

POST https://docs.ton.org/feedback

```json
{
  "path": "/contract-dev/blueprint/coverage",
  "feedback": "Description of the issue"
}
```

Only submit feedback when you have something specific and actionable to report.

</AgentInstructions>

# Collecting test coverage

export const Image = ({src, darkSrc, alt = '', darkAlt, href, target, height = 342, width = 608, noZoom = false, center = false}) => {
  const isSVG = src.match(/\.svg(?:[#?].*?)?$/i) !== null;
  const shouldInvert = isSVG && !darkSrc;
  const shouldCreateLink = href !== undefined;
  const minPx = 9;
  const maxPx = 608;
  const expectedPx = `a number or a string with a number that is greater than ${minPx - 1} and less than or equal to ${maxPx}`;
  const createInvalidPropCallout = (title, received, expected) => {
    return <Danger>
        <span className="font-bold">
          Invalid <code>{title.toString()}</code> passed!
        </span>
        <br />
        <span className="font-bold">Received: </span>
        {received.toString()}
        <br />
        <span className="font-bold">Expected: </span>
        {expected.toString()}
        {}
      </Danger>;
  };
  const checkValidDimensionValue = value => {
    switch (typeof value) {
      case "string":
      case "number":
        const num = Number(value);
        return Number.isSafeInteger(num) && num >= minPx && num <= maxPx;
      default:
        return false;
    }
  };
  let callouts = [];
  if (height && !checkValidDimensionValue(height)) {
    callouts.push(createInvalidPropCallout("height", height, expectedPx));
  }
  if (width && !checkValidDimensionValue(width)) {
    callouts.push(createInvalidPropCallout("width", width, expectedPx));
  }
  if (callouts.length !== 0) {
    return callouts;
  }
  const heightPx = Number(height);
  const widthPx = Number(width);
  const shouldCenter = center === "true" || center === true ? true : false;
  const shouldNotZoom = noZoom === "true" || noZoom === true ? true : false;
  const images = <>
      <img className="block dark:hidden" src={src} alt={alt} {...height && ({
    height: heightPx
  })} {...width && ({
    width: widthPx
  })} {...(shouldCreateLink || shouldInvert || shouldNotZoom) && ({
    noZoom: "true"
  })} />
      <img className={`hidden dark:block ${shouldInvert ? "invert" : ""}`} src={darkSrc ?? src} alt={darkAlt ?? alt} {...height && ({
    height: heightPx
  })} {...width && ({
    width: widthPx
  })} {...(shouldCreateLink || shouldInvert || shouldNotZoom) && ({
    noZoom: "true"
  })} />
    </>;
  if (shouldCreateLink) {
    if (shouldCenter) {
      return <div style={{
        display: "flex",
        justifyContent: "center"
      }}>
          <a href={href} target={target ?? "_self"}>
            {images}
          </a>
        </div>;
    }
    return <a href={href} target={target ?? "_self"}>
        {images}
      </a>;
  }
  if (shouldCenter) {
    return <div style={{
      display: "flex",
      justifyContent: "center"
    }}>{images}</div>;
  }
  return images;
};

export const Aside = ({type = "note", title = "", icon = "", iconType = "regular", children}) => {
  const asideVariants = ["note", "tip", "caution", "danger"];
  const asideComponents = {
    note: {
      outerStyle: "border-sky-500/20 bg-sky-50/50 dark:border-sky-500/30 dark:bg-sky-500/10",
      innerStyle: "text-sky-900 dark:text-sky-200",
      calloutType: "note",
      icon: <svg width="14" height="14" viewBox="0 0 14 14" fill="currentColor" xmlns="http://www.w3.org/2000/svg" className="w-4 h-4 text-sky-500" aria-label="Note">
          <path fill-rule="evenodd" clip-rule="evenodd" d="M7 1.3C10.14 1.3 12.7 3.86 12.7 7C12.7 10.14 10.14 12.7 7 12.7C5.48908 12.6974 4.0408 12.096 2.97241 11.0276C1.90403 9.9592 1.30264 8.51092 1.3 7C1.3 3.86 3.86 1.3 7 1.3ZM7 0C3.14 0 0 3.14 0 7C0 10.86 3.14 14 7 14C10.86 14 14 10.86 14 7C14 3.14 10.86 0 7 0ZM8 3H6V8H8V3ZM8 9H6V11H8V9Z"></path>
        </svg>
    },
    tip: {
      outerStyle: "border-emerald-500/20 bg-emerald-50/50 dark:border-emerald-500/30 dark:bg-emerald-500/10",
      innerStyle: "text-emerald-900 dark:text-emerald-200",
      calloutType: "tip",
      icon: <svg width="11" height="14" viewBox="0 0 11 14" fill="currentColor" xmlns="http://www.w3.org/2000/svg" className="text-emerald-600 dark:text-emerald-400/80 w-3.5 h-auto" aria-label="Tip">
          <path d="M3.12794 12.4232C3.12794 12.5954 3.1776 12.7634 3.27244 12.907L3.74114 13.6095C3.88471 13.8248 4.21067 14 4.46964 14H6.15606C6.41415 14 6.74017 13.825 6.88373 13.6095L7.3508 12.9073C7.43114 12.7859 7.49705 12.569 7.49705 12.4232L7.50055 11.3513H3.12521L3.12794 12.4232ZM5.31288 0C2.52414 0.00875889 0.5 2.26889 0.5 4.78826C0.5 6.00188 0.949566 7.10829 1.69119 7.95492C2.14321 8.47011 2.84901 9.54727 3.11919 10.4557C3.12005 10.4625 3.12175 10.4698 3.12261 10.4771H7.50342C7.50427 10.4698 7.50598 10.463 7.50684 10.4557C7.77688 9.54727 8.48281 8.47011 8.93484 7.95492C9.67728 7.13181 10.1258 6.02703 10.1258 4.78826C10.1258 2.15486 7.9709 0.000106649 5.31288 0ZM7.94902 7.11267C7.52078 7.60079 6.99082 8.37878 6.6077 9.18794H4.02051C3.63739 8.37878 3.10743 7.60079 2.67947 7.11294C2.11997 6.47551 1.8126 5.63599 1.8126 4.78826C1.8126 3.09829 3.12794 1.31944 5.28827 1.3126C7.2435 1.3126 8.81315 2.88226 8.81315 4.78826C8.81315 5.63599 8.50688 6.47551 7.94902 7.11267ZM4.87534 2.18767C3.66939 2.18767 2.68767 3.16939 2.68767 4.37534C2.68767 4.61719 2.88336 4.81288 3.12521 4.81288C3.36705 4.81288 3.56274 4.61599 3.56274 4.37534C3.56274 3.6515 4.1515 3.06274 4.87534 3.06274C5.11719 3.06274 5.31288 2.86727 5.31288 2.62548C5.31288 2.38369 5.11599 2.18767 4.87534 2.18767Z"></path>
        </svg>
    },
    caution: {
      outerStyle: "border-amber-500/20 bg-amber-50/50 dark:border-amber-500/30 dark:bg-amber-500/10",
      innerStyle: "text-amber-900 dark:text-amber-200",
      calloutType: "warning",
      icon: <svg className="flex-none w-5 h-5 text-amber-400 dark:text-amber-300/80" fill="none" viewBox="0 0 24 24" stroke="currentColor" stroke-width="2" aria-label="Warning">
          <path stroke-linecap="round" stroke-linejoin="round" d="M12 9v2m0 4h.01m-6.938 4h13.856c1.54 0 2.502-1.667 1.732-3L13.732 4c-.77-1.333-2.694-1.333-3.464 0L3.34 16c-.77 1.333.192 3 1.732 3z"></path>
        </svg>
    },
    danger: {
      outerStyle: "border-red-500/20 bg-red-50/50 dark:border-red-500/30 dark:bg-red-500/10",
      innerStyle: "text-red-900 dark:text-red-200",
      calloutType: "danger",
      icon: <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" fill="currentColor" className="text-red-600 dark:text-red-400/80 w-4 h-4" aria-label="Danger">
          <path d="M17.1 292c-12.9-22.3-12.9-49.7 0-72L105.4 67.1c12.9-22.3 36.6-36 62.4-36l176.6 0c25.7 0 49.5 13.7 62.4 36L494.9 220c12.9 22.3 12.9 49.7 0 72L406.6 444.9c-12.9 22.3-36.6 36-62.4 36l-176.6 0c-25.7 0-49.5-13.7-62.4-36L17.1 292zm41.6-48c-4.3 7.4-4.3 16.6 0 24l88.3 152.9c4.3 7.4 12.2 12 20.8 12l176.6 0c8.6 0 16.5-4.6 20.8-12L453.4 268c4.3-7.4 4.3-16.6 0-24L365.1 91.1c-4.3-7.4-12.2-12-20.8-12l-176.6 0c-8.6 0-16.5 4.6-20.8 12L58.6 244zM256 128c13.3 0 24 10.7 24 24l0 112c0 13.3-10.7 24-24 24s-24-10.7-24-24l0-112c0-13.3 10.7-24 24-24zM224 352a32 32 0 1 1 64 0 32 32 0 1 1 -64 0z"></path>
        </svg>
    }
  };
  let variant = type;
  let gotInvalidVariant = false;
  if (!asideVariants.includes(type)) {
    gotInvalidVariant = true;
    variant = "danger";
  }
  const iconVariants = ["regular", "solid", "light", "thin", "sharp-solid", "duotone", "brands"];
  if (!iconVariants.includes(iconType)) {
    iconType = "regular";
  }
  return <>
      <div className={`callout my-4 px-5 py-4 overflow-hidden rounded-2xl flex gap-3 border ${asideComponents[variant].outerStyle}`} data-callout-type={asideComponents[variant].calloutType}>
        <div className="mt-0.5 w-4" data-component-part="callout-icon">
          {}
          {icon === "" ? asideComponents[variant].icon : <Icon icon={icon} iconType={iconType} size={14} />}
        </div>
        <div className={`text-sm prose min-w-0 w-full ${asideComponents[variant].innerStyle}`} data-component-part="callout-content">
          {gotInvalidVariant ? <p>
              <span className="font-bold">
                Invalid <code>type</code> passed!
              </span>
              <br />
              <span className="font-bold">Received: </span>
              {type}
              <br />
              <span className="font-bold">Expected one of: </span>
              {asideVariants.join(", ")}
            </p> : <>
              {title && <p className="font-bold">{title}</p>}
              {children}
            </>}
        </div>
      </div>
    </>;
};

<Aside>
  This page covers coverage calculated on TVM assembly instructions. Path- and source-line coverage is not implemented.
</Aside>

There are two main ways to calculate coverage of your `@ton/sandbox` tests.

## Easy way

<Aside type="caution" title="Library compatibility">
  For this way to work correctly, a version of `@ton/sandbox >= 0.37.2` and `@ton/blueprint >= 0.41.0` is needed.
</Aside>

When using Blueprint, the only thing you need to collect coverage is to run the following command:

```bash theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
blueprint test --coverage
```

Results will appear in the `coverage/` directory as HTML files with reports for each of your contracts.

## Customizable way

There might be some reasons why you don't want to simply use `--coverage`.

* You don't want to collect coverage for all contracts.
* You use `@ton/sandbox` but don't use `@ton/blueprint`.
* Not all contracts have source code. (For example, for each transaction, you deploy a new contract, and you don't have wrappers for it.)
* You want to get the raw data and customize the output.

### 1. Enable coverage collection

Before running tests, add `blockchain.enableCoverage()` to collect coverage data:

```typescript theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
import {Blockchain} from '@ton/sandbox';

describe('Contract Tests', () => {
    let blockchain: Blockchain;
    let contract: SandboxContract<MyContract>;

    beforeEach(async () => {
        blockchain = await Blockchain.create();

        blockchain.enableCoverage();
        // or for COVERAGE=true mode only
        // blockchain.enableCoverage(process.env["COVERAGE"] === "true");

        // Deploy your contract
        contract = blockchain.openContract(MyContract.fromInit());
        // ... deployment logic
    });

    // Your tests here...
});
```

### 2. Collect coverage after tests

```typescript theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
afterAll(() => {
    const coverage = blockchain.coverage(contract);
    console.log(coverage?.summary());
})
```

### 3. Generate reports

```typescript theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
import {writeFileSync} from 'fs';

afterAll(() => {
    const coverage = blockchain.coverage(contract);
    if (!coverage) return;

    // Generate HTML report for detailed analysis
    const htmlReport = coverage.report("html");
    writeFileSync("coverage.html", htmlReport);

    // Print text report to console
    const textReport = coverage.report("text");
    console.log(textReport);
});
```

## Understanding coverage data

### Coverage summary

The coverage summary provides key metrics about your test coverage:

```typescript theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
const summary = coverage.summary();

console.log(`Total lines: ${summary.totalLines}`);
console.log(`Covered lines: ${summary.coveredLines}`);
console.log(`Coverage percentage: ${summary.coveragePercentage.toFixed(2)}%`);
console.log(`Total gas consumed: ${summary.totalGas}`);
console.log(`Total hits: ${summary.totalHits}`);

// Instruction-level statistics
summary.instructionStats.forEach(stat => {
    console.log(`${stat.name}: ${stat.totalHits} hits, ${stat.totalGas} gas, avg ${stat.avgGas}`);
});
```

### Coverage reports

* **HTML Report**: Interactive report with highlighting and line-by-line coverage details
* **Text Report**: Console-friendly report with coverage information and marked code

## Advanced usage patterns

### Multiple test suites

When running multiple test files, you might want to merge coverage data:

```typescript theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
// In first test file
const coverage1 = blockchain.coverage(contract);
if (!coverage1) return;
const coverage1Json = coverage1.toJson();
writeFileSync("coverage1.json", coverage1Json);

// In second test file
const coverage2 = blockchain.coverage(contract);
if (!coverage2) return;
const coverage2Json = coverage2.toJson();
writeFileSync("coverage2.json", coverage2Json);

// Merge coverage data in separate script after tests
const savedCoverage1 = Coverage.fromJson(readFileSync("coverage1.json", "utf-8"));
const savedCoverage2 = Coverage.fromJson(readFileSync("coverage2.json", "utf-8"));
const totalCoverage = savedCoverage1.mergeWith(savedCoverage2);

console.log(`Combined coverage: ${totalCoverage.summary().coveragePercentage}%`);
```

## Coverage for multiple contracts

When testing systems with multiple contracts:

```typescript not runnable theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
describe('Multi-Contract System', () => {
    let blockchain: Blockchain;
    let contract1: SandboxContract<Contract1>;
    let contract2: SandboxContract<Contract2>;

    beforeEach(async () => {
        blockchain = await Blockchain.create();
        blockchain.enableCoverage();

        // Deploy multiple contracts
        contract1 = blockchain.openContract(Contract1.fromInit());
        contract2 = blockchain.openContract(Contract2.fromInit());
    });

    afterAll(() => {
        // Get coverage for each contract separately
        const coverage1 = blockchain.coverage(contract1);
        const coverage2 = blockchain.coverage(contract2);

        if (!coverage1 || !coverage2) return;

        console.log('Contract 1 Coverage:', coverage1.summary().coveragePercentage);
        console.log('Contract 2 Coverage:', coverage2.summary().coveragePercentage);

        // Generate separate reports
        writeFileSync("contract1-coverage.html", coverage1.report("html"));
        writeFileSync("contract2-coverage.html", coverage2.report("html"));
    });
});
```

## Interpret results

The usual report looks like this:

<Image src="/resources/images/coverage-report.png" />

Apart from the header statistics, the line-by-line coverage report is the most informative. Most fields are self‑explanatory; the code section shows per‑instruction hit counts (blue) and gas cost (red). This helps you analyze both coverage and gas efficiency.

<Aside>
  To understand the TVM assembly output, read [TVM](/foundations/whitepapers/tvm).
</Aside>

## Limitations

Note that when code of other contracts is stored directly in the code of the contract ([Tact](/languages/tact) does that automatically if a contract system does not contain circular dependencies), that affects the overall code coverage percentage.

To mitigate this effect in coverage estimation, add a circular dependency. For example, import a file with the following content.

```tact title="Tact" theme={"theme":{"light":"github-light-default","dark":"dark-plus"},"languages":{"custom":["/resources/grammars/tolk.tmLanguage.json","/resources/grammars/tlb.tmLanguage.json","/resources/grammars/fift.tmLanguage.json","/resources/grammars/tasm.tmLanguage.json","/resources/grammars/func.tmLanguage.json"]}}
contract A {
    receive() {
        let x = initOf B();
        drop2(x);
    }
}

contract B() {
    receive() {
        let x = initOf A();
        drop2(x);
    }
}

asm fun drop2(x: StateInit) {
    DROP2
}
```