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JMockit is a Java toolkit for automated developer testing. It contains APIs for the creation of the objects to be tested, for mocking dependencies, and for faking external APIs; JUnit (4 & 5) and TestNG test runners are supported. It also contains an advanced code coverage tool.

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/*
 * Copyright (c) 2006 JMockit developers
 * This file is subject to the terms of the MIT license (see LICENSE.txt).
 */
package mockit.internal.util;

import edu.umd.cs.findbugs.annotations.NonNull;

import java.io.IOException;

/**
 * Provides utility methods to extract and filter stack trace information.
 */
public final class StackTrace {
    @NonNull
    private final Throwable throwable;
    @NonNull
    private StackTraceElement[] elements;

    public StackTrace(@NonNull Throwable throwable) {
        this.throwable = throwable;
        elements = throwable.getStackTrace();
    }

    public int getDepth() {
        return elements.length;
    }

    @NonNull
    public StackTraceElement getElement(int index) {
        return elements[index];
    }

    public static void filterStackTrace(@NonNull Throwable t) {
        new StackTrace(t).filter();
    }

    public void filter() {
        StackTraceElement[] filteredST = new StackTraceElement[elements.length];
        int i = 0;

        for (StackTraceElement ste : elements) {
            if (ste.getFileName() != null) {
                String where = ste.getClassName();

                if (!isJDKOr3rdPartyLibraryInternalMethod(ste) && !isTestFrameworkMethod(where)
                        && !isJMockitMethod(where)) {
                    filteredST[i] = ste;
                    i++;
                }
            }
        }

        StackTraceElement[] newStackTrace = new StackTraceElement[i];
        System.arraycopy(filteredST, 0, newStackTrace, 0, i);
        throwable.setStackTrace(newStackTrace);
        elements = newStackTrace;

        Throwable cause = throwable.getCause();

        if (cause != null) {
            new StackTrace(cause).filter();
        }
    }

    private static boolean isJDKOr3rdPartyLibraryInternalMethod(@NonNull StackTraceElement ste) {
        String className = ste.getClassName();

        return className.startsWith("sun.") && !ste.isNativeMethod() || className.startsWith("jdk.")
                || className.startsWith("java.util.") || className.contains(".reflect.")
                || className.contains(".surefire.") || className.contains(".gradle.")
                || className.contains(".intellij.") || className.contains(".jdt.");
    }

    private static boolean isTestFrameworkMethod(@NonNull String where) {
        return where.startsWith("org.junit.") || where.startsWith("org.testng.");
    }

    private static boolean isJMockitMethod(@NonNull String where) {
        if (!where.startsWith("mockit.")) {
            return false;
        }

        int p = where.indexOf('$');

        if (p < 0) {
            int q = where.lastIndexOf("Test");
            return q < 0 || q + 4 < where.length();
        }

        int q = where.lastIndexOf("Test", p - 4);

        if (q < 0) {
            return true;
        }

        q += 4;
        return q < where.length() && where.charAt(q) != '$';
    }

    public void print(@NonNull Appendable output) {
        String previousFileName = null;
        int previousLineNumber = 0;
        String sep = "";

        for (int i = 0, d = getDepth(); i < d; i++) {
            StackTraceElement ste = elements[i];

            if (ste.getLineNumber() != previousLineNumber || !ste.getFileName().equals(previousFileName)) {
                try {
                    output.append(sep).append("\tat ").append(ste.toString());
                } catch (IOException ignore) {
                }
                sep = "\n";
                previousFileName = ste.getFileName();
                previousLineNumber = ste.getLineNumber();
            }
        }
    }
}