diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index a029037f4f..c93c4539fd 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -49,6 +49,24 @@ jobs:
           verbose: true # optional (default = false)
         if: runner.os == 'Linux'
 
+  standalone-lfc-tests:
+    strategy:
+      matrix:
+        platform: [ubuntu-latest, macos-latest, windows-latest]
+    runs-on: ${{ matrix.platform }}
+    steps:
+      # Setup Build dependencies
+      - name: Setup Java JDK
+        uses: actions/setup-java@v1.4.3
+        with:
+          # The Java version to make available on the path. Takes a whole or semver Java version, or 1.x syntax (e.g. 1.8 => Java 8.x). Early access versions can be specified in the form of e.g. 14-ea, 14.0.0-ea, or 14.0.0-ea.28
+          java-version: 11
+      # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
+      - uses: actions/checkout@v2
+      - name: Run standalone LFC tests
+        run: |
+          ./gradlew :org.lflang.lfc:test --stacktrace
+
   c-tests:
     strategy:
       matrix:
diff --git a/build.gradle b/build.gradle
index 45bdaae265..9fca3c366e 100644
--- a/build.gradle
+++ b/build.gradle
@@ -66,3 +66,18 @@ subprojects {
 		delete "${projectDir}/src-gen/"
 	}
 }
+
+gradle.projectsEvaluated {
+	// Our CI uses --tests filters, which fails if some
+	// subprojects have no matching test.
+	//
+	// https://stackoverflow.com/questions/26147480/how-to-make-gradle-not-to-mark-build-failed-if-no-tests-are-found
+	subprojects {
+		test {
+			filter {
+				setFailOnNoMatchingTests(false)
+			}
+		}
+	}
+}
+
diff --git a/org.lflang.lfc/build.gradle b/org.lflang.lfc/build.gradle
index f96d08da49..ad4b8b1a36 100644
--- a/org.lflang.lfc/build.gradle
+++ b/org.lflang.lfc/build.gradle
@@ -1,7 +1,28 @@
+
+sourceSets {
+    test {
+        java.srcDirs = []
+        kotlin.srcDirs = ['test/kotlin']
+        resources.srcDir('test/resources')
+        resources.include '**/*'
+    }
+}
+
+compileTestKotlin {
+    destinationDir = compileTestJava.destinationDir
+    kotlinOptions {
+        jvmTarget = "1.8"
+    }
+}
+
+
+
 dependencies {
     implementation project(':org.lflang')
     implementation "org.eclipse.xtext:org.eclipse.xtext.ide:${xtextVersion}"
     implementation "org.eclipse.xtext:org.eclipse.xtext.xbase.ide:${xtextVersion}"
+
+    testImplementation "junit:junit:4.12"
 }
 
 apply plugin: 'application'
diff --git a/org.lflang.lfc/src/org/lflang/lfc/LFStandaloneModule.java b/org.lflang.lfc/src/org/lflang/lfc/LFStandaloneModule.java
index 01215fef69..a26878335d 100644
--- a/org.lflang.lfc/src/org/lflang/lfc/LFStandaloneModule.java
+++ b/org.lflang.lfc/src/org/lflang/lfc/LFStandaloneModule.java
@@ -26,15 +26,16 @@
  * generated by Xtext 2.23.0
  */
 
-package org.lflang;
+package org.lflang.lfc;
 
 import java.util.Objects;
 
+import org.eclipse.emf.ecore.EValidator;
+import org.eclipse.emf.ecore.impl.EValidatorRegistryImpl;
 import org.eclipse.xtext.validation.ValidationMessageAcceptor;
 
-import org.lflang.lfc.ReportingBackend;
-import org.lflang.lfc.StandaloneErrorReporter;
-import org.lflang.lfc.StandaloneIssueAcceptor;
+import org.lflang.ErrorReporter;
+import org.lflang.LFRuntimeModule;
 
 import com.google.inject.Binder;
 import com.google.inject.Module;
@@ -60,5 +61,13 @@ public void configure(Binder binder) {
         binder.bind(ErrorReporter.class).to(StandaloneErrorReporter.class);
         binder.bind(ReportingBackend.class).toInstance(helper);
         binder.bind(ValidationMessageAcceptor.class).to(StandaloneIssueAcceptor.class);
+        // This is required to force the ResourceValidator to
+        // use a new registry instance (which is reused by the injector as a singleton).
+        // Otherwise, it uses the static EValidator.Registry.INSTANCE which is bad
+        // as the first validator to be created would persist in that static instance.
+        // New injectors would reuse the existing instance, but
+        // its fields would have been injected by an older injector
+        // and be out of sync with the rest of the application.
+        binder.bind(EValidator.Registry.class).to(EValidatorRegistryImpl.class).asEagerSingleton();
     }
 }
diff --git a/org.lflang.lfc/src/org/lflang/lfc/Main.java b/org.lflang.lfc/src/org/lflang/lfc/Main.java
index 9be18191e7..307c75a396 100644
--- a/org.lflang.lfc/src/org/lflang/lfc/Main.java
+++ b/org.lflang.lfc/src/org/lflang/lfc/Main.java
@@ -39,9 +39,9 @@
 import org.lflang.ErrorReporter;
 import org.lflang.FileConfig;
 import org.lflang.LFRuntimeModule;
-import org.lflang.LFStandaloneModule;
 import org.lflang.LFStandaloneSetup;
 import org.lflang.generator.StandaloneContext;
+import org.lflang.lfc.LFStandaloneModule;
 
 import com.google.inject.Inject;
 import com.google.inject.Injector;
@@ -61,7 +61,7 @@ public class Main {
     private static String MAIN_PATH_IN_JAR = String.join("/",
                                                          new String[] {"!", "org", "lflang", "lfc", "Main.class"});
 
-    
+
     /**
      * Object for interpreting command line arguments.
      */
@@ -87,13 +87,13 @@ public class Main {
      */
     @Inject
     private Provider<ResourceSet> resourceSetProvider;
-    
+
     /**
      * Injected resource validator.
      */
     @Inject
     private IResourceValidator validator;
-    
+
     /**
      * Injected code generator.
      */
@@ -140,20 +140,20 @@ enum CLIOption {
         OUTPUT_PATH("o", "output-path", true, false, "Specify the root output directory.", false),
         RUNTIME_VERSION(null, "runtime-version", true, false, "Specify the version of the runtime library used for compiling LF programs.", true),
         EXTERNAL_RUNTIME_PATH(null, "external-runtime-path", true, false, "Specify an external runtime library to be used by the compiled binary.", true);
-        
+
         /**
          * The corresponding Apache CLI Option object.
          */
         public final Option option;
-        
+
         /**
          * Whether or not to pass this option to the code generator.
          */
         public final boolean passOn;
-        
+
         /**
          * Construct a new CLIOption.
-         * 
+         *
          * @param opt         The short option name. E.g.: "f" denotes a flag
          *                    "-f".
          * @param longOpt     The long option name. E.g.: "foo" denotes a flag
@@ -171,10 +171,10 @@ enum CLIOption {
             option.setRequired(isReq);
             this.passOn = passOn;
         }
-    
+
         /**
          * Create an Apache Commons CLI Options object and add all the options.
-         * 
+         *
          * @return Options object that includes all the options in this enum.
          */
         public static Options getOptions() {
@@ -182,11 +182,11 @@ public static Options getOptions() {
             Arrays.asList(CLIOption.values()).forEach(o -> opts.addOption(o.option));
             return opts;
         }
-        
+
         /**
          * Return a list of options that are to be passed on to the code
          * generator.
-         * 
+         *
          * @return List of options that must be passed on to the code gen stage.
          */
         public static List<Option> getPassedOptions() {
@@ -194,7 +194,7 @@ public static List<Option> getPassedOptions() {
                          .filter(opt -> opt.passOn).map(opt -> opt.option)
                          .collect(Collectors.toList());
         }
-        
+
     }
 
     /**
@@ -204,7 +204,7 @@ public static List<Option> getPassedOptions() {
     private boolean mustUpdate() {
         return cmd.hasOption(CLIOption.UPDATE.option.getOpt());
     }
-    
+
     /**
      * Indicate whether or not a rebuild must occur.
      * @return whether or not the rebuild or update flag is present.
@@ -212,7 +212,7 @@ private boolean mustUpdate() {
     private boolean mustRebuild() {
         return mustUpdate() || cmd.hasOption(CLIOption.REBUILD.option.getOpt());
     }
-    
+
     /**
      * Main function of the stand-alone compiler.
      * @param args CLI arguments
@@ -248,17 +248,17 @@ public static void main(final String[] args) {
 
         try {
             main.cmd = parser.parse(options, args, true);
-            
+
             if (main.cmd.hasOption(CLIOption.HELP.option.getOpt())) {
                 formatter.printHelp("lfc", options);
                 System.exit(0);
             }
-            
+
             // If the rebuild flag is not used, or if it is used but the jar
             // is not out of date, continue with the normal flow of execution.
             if (!main.mustRebuild() || (main.mustRebuild() && !main.rebuildAndFork())) {
                 List<String> files = main.cmd.getArgList();
-                
+
                 if (files.size() < 1) {
                     reporter.printFatalErrorAndExit("No input files.");
                 }
@@ -275,12 +275,12 @@ public static void main(final String[] args) {
             System.exit(1);
         }
     }
-    
+
     /**
      * Fork off a new process (that is an execution of a freshly rebuilt jar)
      * and wait for it to return.
-     * 
-     * @param cmd The CommandLine object that has stored in it the CLI 
+     *
+     * @param cmd The CommandLine object that has stored in it the CLI
      * arguments of the parent process, to be passed on to the child process.
      */
     private void forkAndWait(CommandLine cmd) {
@@ -310,18 +310,18 @@ private void forkAndWait(CommandLine cmd) {
         } catch (InterruptedException e) {
             reporter.printError("Child process was interupted. Exiting.");
         }
-        
+
     }
-    
+
     private boolean modifiedFilesExist(Path start, long mod) throws IOException {
         return ((Files.find(start, Integer.MAX_VALUE,
                 (path, attr) -> (attr.lastModifiedTime()
                         .compareTo(FileTime.fromMillis(mod)) > 0))).count() > 0);
     }
-    
+
     /**
      * Indicate whether or not there is any work to do.
-     * 
+     *
      * @return True if a rebuild is necessary, false otherwise.
      */
     private boolean needsUpdate() {
@@ -336,7 +336,7 @@ private boolean needsUpdate() {
         }
         return outOfDate;
     }
-    
+
     /**
      * Rebuild and return. If the rebuilding failed, exit.
      */
@@ -353,12 +353,12 @@ private void rebuildOrExit() {
         }
         ProcessBuilder build = new ProcessBuilder(cmdList);
         build.directory(rootPath.toFile());
-    
+
         try {
             Process p = build.start();
             // Read the output from the build.
             String result = new String(p.getInputStream().readAllBytes());
-            
+
             p.waitFor();
             if (p.exitValue() == 0) {
                 reporter.printInfo("Rebuild successful; forking off updated version of lfc.");
@@ -369,7 +369,7 @@ private void rebuildOrExit() {
             reporter.printFatalErrorAndExit("Rebuild failed. Reason: " + e.getMessage());
         }
     }
-    
+
     /**
      * Rebuild and fork if an update is needed. If the rebuild was successful,
      * return true. If no update was needed, return false. If the rebuild was
@@ -389,7 +389,7 @@ private boolean rebuildAndFork() {
         }
         return true;
     }
-  
+
     /**
      * Store arguments as properties, to be passed on to the generator.
      */
@@ -465,7 +465,7 @@ private void runGenerator(List<Path> files, Injector injector) {
             this.fileAccess.setOutputPath(resolved);
 
             final Resource resource = getValidatedResource(path);
-            
+
             exitIfCollectedErrors();
 
             StandaloneContext context = new StandaloneContext();
@@ -491,44 +491,55 @@ private void runGenerator(List<Path> files, Injector injector) {
     private void exitIfCollectedErrors() {
         if (issueCollector.getErrorsOccurred()) {
             // if there are errors, don't print warnings.
-            List<LfIssue> errors = issueCollector.getErrors();
-            errors.forEach(reporter::printIssue);
+            List<LfIssue> errors = printErrorsIfAny();
             String cause = errors.size() == 1 ? "previous error"
                                               : errors.size() + " previous errors";
             reporter.printFatalErrorAndExit("Aborting due to " + cause);
         }
     }
-    
+
+    // visible in tests
+    public List<LfIssue> printErrorsIfAny() {
+        List<LfIssue> errors = issueCollector.getErrors();
+        errors.forEach(reporter::printIssue);
+        return errors;
+    }
+
     /**
      * Given a path, obtain a resource and validate it. If issues arise during validation,
      * these are recorded using the issue collector.
-     * 
+     *
      * @param path Path to the resource to validate.
      * @return A validated resource
      */
-    private Resource getValidatedResource(Path path) {
-        final ResourceSet set = this.resourceSetProvider.get();
-        final Resource resource =
-            set.getResource(URI.createFileURI(path.toString()), true);
+    // visible in tests
+    public Resource getValidatedResource(Path path) {
+        final Resource resource = getResource(path);
 
-        if (cmd.hasOption(CLIOption.FEDERATED.option.getOpt())) {
+        if (cmd != null && cmd.hasOption(CLIOption.FEDERATED.option.getOpt())) {
             if (!ASTUtils.makeFederated(resource)) {
                 reporter.printError("Unable to change main reactor to federated reactor.");
             }
         }
 
         List<Issue> issues = this.validator.validate(resource, CheckMode.ALL, CancelIndicator.NullImpl);
-        
+
         for (Issue issue : issues) {
             URI uri = issue.getUriToProblem(); // Issues may also relate to imported resources.
             try {
-                issueCollector.accept(new LfIssue(issue.getMessage(),
-                    issue.getSeverity(), issue.getLineNumber(),
-                    issue.getColumn(), issue.getLength(), FileConfig.toPath(uri)));
+                issueCollector.accept(new LfIssue(issue.getMessage(), issue.getSeverity(),
+                                                  issue.getLineNumber(), issue.getColumn(),
+                                                  issue.getLineNumberEnd(), issue.getColumnEnd(),
+                                                  issue.getLength(), FileConfig.toPath(uri)));
             } catch (IOException e) {
-                reporter.printError("Unable to convert '" + uri + "' to path.");
+                reporter.printError("Unable to convert '" + uri + "' to path." + e);
             }
         }
         return resource;
     }
+
+    public Resource getResource(Path path) {
+        final ResourceSet set = this.resourceSetProvider.get();
+        return set.getResource(URI.createFileURI(path.toString()), true);
+    }
 }
diff --git a/org.lflang.lfc/src/org/lflang/lfc/ReportingUtil.kt b/org.lflang.lfc/src/org/lflang/lfc/ReportingUtil.kt
index fb69bf76ad..f989dfdae4 100644
--- a/org.lflang.lfc/src/org/lflang/lfc/ReportingUtil.kt
+++ b/org.lflang.lfc/src/org/lflang/lfc/ReportingUtil.kt
@@ -34,6 +34,8 @@ import java.nio.file.Files
 import java.nio.file.Path
 import java.nio.file.Paths
 import java.util.*
+import java.util.Collections.nCopies
+import kotlin.collections.ArrayList
 import kotlin.math.max
 import kotlin.math.min
 import kotlin.system.exitProcess
@@ -83,6 +85,8 @@ data class LfIssue(
     val severity: Severity,
     val line: Int?,
     val column: Int?,
+    val endLine: Int?,
+    val endColumn: Int?,
     val length: Int?,
     val file: Path?
 ) : Comparable<LfIssue> {
@@ -145,11 +149,11 @@ class ReportingBackend constructor(
      * messages when printing a code snippet from the file
      * in which the error originated.
      */
-    private val numLinesAround: Int,
+    private val numLinesAround: Int = 2,
 ) {
     /** Secondary constructor with default arguments and marked with @Inject */
     @Inject
-    constructor(io: Io) : this(io, AnsiColors(true), 2)
+    constructor(io: Io) : this(io, AnsiColors(true))
 
     /** *Absolute* path to lines. */
     private val fileCache = mutableMapOf<Path, List<String>?>()
@@ -159,7 +163,10 @@ class ReportingBackend constructor(
         if (path == null) null
         else fileCache.computeIfAbsent(path.toAbsolutePath()) {
             try {
-                Files.readAllLines(it, StandardCharsets.UTF_8)
+                Files.readAllLines(it, StandardCharsets.UTF_8) +
+                        // Add a bunch of fake empty lines at the end to avoid IndexOutOfBoundsException
+                        // with errors that hit EOF.
+                        nCopies(5, "")
             } catch (e: IOException) {
                 null
             }
@@ -205,7 +212,7 @@ class ReportingBackend constructor(
 
         val header = severity.name.toLowerCase(Locale.ROOT)
 
-        var fullMessage: String = this.header + colors.severityColors(header, severity) + colors.bold(": " + issue.message) + "\n"
+        var fullMessage: String = this.header + colors.severityColors(header, severity) + colors.bold(": " + issue.message) + System.lineSeparator()
         val snippet: String? = filePath?.let { formatIssue(issue, filePath) }
 
         if (snippet == null) {
@@ -236,11 +243,11 @@ class ReportingBackend constructor(
     }
 
     private fun getBuilder(issue: LfIssue, lines: List<String>, displayPath: String): MessageTextBuilder {
-        val zeroL = issue.line!! - 1
-        val firstL = max(0, zeroL - numLinesAround + 1)
-        val lastL = min(lines.size, zeroL + numLinesAround)
-        val strings: List<String> = lines.subList(firstL, lastL)
-        return MessageTextBuilder(strings, firstL, zeroL - firstL, displayPath, issue)
+        val firstL = (issue.line!! - numLinesAround).coerceIn(0..lines.size)
+        val lastL = (issue.endLine!! - 1 + numLinesAround).coerceIn(0..lines.size)
+        val lineRange: List<String> = lines.subList(firstL, lastL)
+        val errorIdxInLineRange = issue.line - 1 - firstL
+        return MessageTextBuilder(lineRange, firstL, errorIdxInLineRange, displayPath, issue)
     }
 
     /** Renders a single issue. */
@@ -255,24 +262,40 @@ class ReportingBackend constructor(
     ) {
 
         init {
-            assert(0 <= errorIdx && errorIdx < lines.size) { "Weird indices --- first=$first, errorIdx=$errorIdx, lines=$lines" }
+            assert(errorIdx in 0..lines.size) { "Weird indices --- first=$first, errorIdx=$errorIdx, lines=$lines" }
         }
 
         fun build(): String {
             // the padding to apply to line numbers
             val pad = 2 + widthOfLargestLineNum()
-            val withLineNums: MutableList<String> =
+            val withLineNums: ArrayList<String> =
                 lines.indices.mapTo(ArrayList()) { numberedLine(it, pad) }
 
-            withLineNums.add(errorIdx + 1, makeErrorLine(pad))
-            withLineNums.add(errorIdx + 2, emptyGutter(pad)) // skip a line
+            if (issue.line!! == issue.endLine!!) {
+                // single line warning
+                withLineNums.add(errorIdx + 1, makeErrorLine(pad))
+                withLineNums.add(errorIdx + 2, emptyGutter(pad)) // skip a line
+            } else {
+                // multiline
+                val spanInLines = issue.endLine - issue.line
+
+                withLineNums.add(errorIdx, makeMultilineFence(pad, forward = true))
+                withLineNums.add(errorIdx + spanInLines + 2, makeMultilineFence(pad, forward = false, message = issue.message))
+
+                if (spanInLines >= 3) {
+                    // too big, remove some lines
+                    withLineNums.subList(errorIdx + 3, errorIdx + spanInLines ).clear()
+                    // replace with an ellipsis
+                    withLineNums.add(errorIdx + 3, emptyGutter(pad) + " ...")
+                }
+            }
 
             // skip a line at the beginning
             // add it at the end to not move other indices
             withLineNums.add(0, emptyGutter(pad))
             withLineNums.add(0, makeHeaderLine(pad))
 
-            return withLineNums.joinToString("\n")
+            return withLineNums.joinToString(System.lineSeparator())
         }
 
         private fun widthOfLargestLineNum() = (lines.size + first).toString().length
@@ -288,13 +311,30 @@ class ReportingBackend constructor(
             return "$prefix $fileDisplayName:${issue.line}:${issue.column}"
         }
 
+        private fun makeMultilineFence(pad: Int, forward: Boolean, message: String? = null): String {
+            val char = if (forward) '>' else '<'
+            val fenceWidth =
+                if (!forward && issue.endColumn != null) {
+                    (issue.endColumn - 1).coerceIn(1..FENCE_WIDTH)
+                } else {
+                    FENCE_WIDTH
+                }
+
+            val fence = buildString {
+                append(' ')
+                repeatChar(char, fenceWidth)
+                if (message != null)
+                    append(' ').append(message)
+            }
+            // gutter has its own ANSI stuff so only fence gets severityColors
+            return emptyGutter(pad) + colors.severityColors(fence, issue.severity)
+        }
+
         private fun makeErrorLine(pad: Int): String {
             val line = lines[errorIdx]
+
             // tabs are replaced with spaces to align messages properly
             fun makeOffset(startIdx: Int, length: Int): Int {
-                // note: this is needed because when the issue spans several lines,
-                // startIdx+length may be greater than the line length.
-                // todo implement real way to format multiline issues
                 val endIndex = min(line.length, startIdx + length)
                 val numTabs = line.substring(startIdx, endIndex).count { it == '\t' }
                 return numTabs * (TAB_REPLACEMENT.length - 1)
@@ -303,9 +343,9 @@ class ReportingBackend constructor(
             val tabOffset = makeOffset(0, issue.column!!) // offset up to marker
             val tabSpanOffset = makeOffset(issue.column - 1, issue.length!!) // offset within marker
 
-            val realLen = min(line.length, issue.column + issue.length)
-
-            val caretLine = with(issue) { buildCaretLine(message.trim(), column!! + tabOffset, realLen + tabSpanOffset) }
+            val caretLine = with(issue) {
+                buildCaretLine(message.trim(), column!! + tabOffset, length!! + tabSpanOffset)
+            }
             // gutter has its own ANSI stuff so only caretLine gets severityColors
             return emptyGutter(pad) + colors.severityColors(caretLine, issue.severity)
         }
@@ -320,11 +360,11 @@ class ReportingBackend constructor(
 
         private fun formatLineNum(str: String) = colors.cyanAndBold(str)
 
-        private fun buildCaretLine(message: String, column: Int, rangeLen: Int): String {
-            fun StringBuilder.repeatChar(c: Char, n: Int) {
-                repeat(n) { append(c) }
-            }
+        fun StringBuilder.repeatChar(c: Char, n: Int) {
+            repeat(n) { append(c) }
+        }
 
+        private fun buildCaretLine(message: String, column: Int, rangeLen: Int): String {
             return buildString {
                 repeatChar(' ', column)
                 repeatChar('^', max(rangeLen, 1))
@@ -335,6 +375,7 @@ class ReportingBackend constructor(
 
     companion object {
         const val TAB_REPLACEMENT = "    "
+        const val FENCE_WIDTH = 14
     }
 }
 
diff --git a/org.lflang.lfc/src/org/lflang/lfc/StandaloneErrorReporter.java b/org.lflang.lfc/src/org/lflang/lfc/StandaloneErrorReporter.java
index bc971699fc..d34118a55b 100644
--- a/org.lflang.lfc/src/org/lflang/lfc/StandaloneErrorReporter.java
+++ b/org.lflang.lfc/src/org/lflang/lfc/StandaloneErrorReporter.java
@@ -51,7 +51,7 @@ private String reportWithNode(String message, Severity severity, EObject obj) {
     }
 
     private String reportSimpleFileCtx(String message, Severity severity, Integer line, Path path) {
-        LfIssue issue = new LfIssue(message, severity, line, null, null, path);
+        LfIssue issue = new LfIssue(message, severity, line, 1, line, 1, 0, path);
         issueAcceptor.accept(issue);
         // Return a string that can be inserted into the generated code.
         return message;
diff --git a/org.lflang.lfc/src/org/lflang/lfc/StandaloneIssueAcceptor.java b/org.lflang.lfc/src/org/lflang/lfc/StandaloneIssueAcceptor.java
index b050a968e2..14d81d72bc 100644
--- a/org.lflang.lfc/src/org/lflang/lfc/StandaloneIssueAcceptor.java
+++ b/org.lflang.lfc/src/org/lflang/lfc/StandaloneIssueAcceptor.java
@@ -41,6 +41,8 @@ void accept(Severity severity, String message, EObject object, EStructuralFeatur
             severity,
             diagnostic.getLine(),
             diagnostic.getColumn(),
+            diagnostic.getLineEnd(),
+            diagnostic.getColumnEnd(),
             diagnostic.getLength(),
             getPath(diagnostic)
         );
diff --git a/org.lflang.lfc/test/kotlin/org/lflang/lfc/tests/LfIssueReportingTest.kt b/org.lflang.lfc/test/kotlin/org/lflang/lfc/tests/LfIssueReportingTest.kt
new file mode 100644
index 0000000000..8dee00cf03
--- /dev/null
+++ b/org.lflang.lfc/test/kotlin/org/lflang/lfc/tests/LfIssueReportingTest.kt
@@ -0,0 +1,154 @@
+/*
+ * Copyright (c) 2021, TU Dresden.
+ *
+ * Redistribution and use in source and binary forms, with or without modification,
+ * are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+ * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package org.lflang.lfc.tests
+
+import junit.framework.Assert.assertEquals
+import junit.framework.AssertionFailedError
+import org.junit.Test
+import org.lflang.LFRuntimeModule
+import org.lflang.LFStandaloneSetup
+import org.lflang.lfc.*
+import java.io.*
+import java.nio.charset.StandardCharsets
+import java.nio.file.Files
+import java.nio.file.Path
+import java.nio.file.Paths
+import java.util.*
+
+
+class SpyPrintStream {
+    private val baout = ByteArrayOutputStream()
+    val ps = PrintStream(baout)
+
+    override fun toString(): String = baout.toString(StandardCharsets.UTF_8)
+}
+
+
+class LfIssueReportingTest {
+    /*
+        Note: when executing these tests in Intellij, I get the following error:
+
+            java.lang.SecurityException: class "org.eclipse.core.runtime.IPath"'s
+             signer information does not match signer information of other classes
+             in the same package
+
+        To fix this:
+        - Go into File > Project Structure (CTRL+MAJ+S)
+        - Open the "Modules" tab
+        - Select the module org.lflang/lfc/test in the tree view
+        - Open the "Dependencies" tab
+        - Remove the dependency org.eclipse.platform:org.eclipse.equinox.common (it will have Provided scope)
+     */
+
+
+    @Test
+    fun testSimpleWarning() {
+        doTest(fileBaseName = "simpleWarning")
+    }
+
+    @Test
+    fun testMultilineWarning() {
+        doTest(fileBaseName = "multilineWarning")
+    }
+
+    @Test
+    fun testTwoLineWarning() {
+        doTest(fileBaseName = "twoLineWarning")
+    }
+
+    @Test
+    fun testMultilineWarningTooBig() {
+        doTest(fileBaseName = "multilineWarningTooBig")
+    }
+
+    @Test
+    fun testIssue490() {
+        doTest(fileBaseName = "issue490")
+    }
+
+    @Test
+    fun testTabs() {
+        doTest(fileBaseName = "tabs")
+    }
+
+    @Test
+    fun testEmptyFile() {
+        doTest(fileBaseName = "emptyFile")
+    }
+
+    @Test
+    fun testColors() {
+        doTest(fileBaseName = "colors", useColors = true)
+    }
+
+    /**
+     * Looks for a file named [fileBaseName].lf to validate,
+     * and its sibling [fileBaseName].stderr, which is the
+     * expected output to stderr. Those files are in the test/resources directory
+     */
+    private fun doTest(fileBaseName: String, loader: Class<*> = this::class.java, useColors: Boolean = false) {
+
+
+        val stderr = SpyPrintStream()
+
+        val backend = ReportingBackend(Io(err = stderr.ps), AnsiColors(useColors), 2)
+        val injector = LFStandaloneSetup(LFRuntimeModule(), LFStandaloneModule(backend))
+            .createInjectorAndDoEMFRegistration()
+        val main = injector.getInstance(Main::class.java)
+
+        val packageName = loader.packageName.replace('.', '/')
+        // relative to root of gradle project
+        val lfFile = Paths.get("test/resources/$packageName/$fileBaseName.lf")
+        val expectedPath = Paths.get("test/resources/$packageName/$fileBaseName.stderr")
+
+        assert(Files.exists(lfFile)) { "Missing test file $lfFile" }
+
+        // this side-effects on the ReportingBackend
+        main.getValidatedResource(lfFile)
+        main.printErrorsIfAny()
+
+        val actualOutput = stderr.toString().normalize(lfFile)
+
+        if (!Files.exists(expectedPath)) {
+            val lines = actualOutput.split("\n") // resplit on normalized delimiter
+            Files.write(expectedPath, lines) // write using platform-specific delimiter, will be normalized by Git
+            throw AssertionFailedError("Expected file $expectedPath does not exist, created it. Don't forget to `git add` it.")
+        }
+        val expected = Files.readString(expectedPath)
+
+        assertEquals(expected.normalize(lfFile), actualOutput)
+    }
+
+    /**
+     * Normalize [this] string to be platform independent.
+     * @param lfFile Path to the test lf file
+     */
+    private fun String.normalize(lfFile: Path) =
+        // normalize newlines and remove line-trailing whitespace
+        trim().replace(Regex("\\s+\\R"), "\n")
+            // Replace file path with placeholder. File path is not
+            // rendered the same on linux and windows (forward/backward slash)
+            .replace(lfFile.toString(), "%%%PATH.lf%%%")
+
+}
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/colors.lf b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/colors.lf
new file mode 100644
index 0000000000..90423dfcb5
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/colors.lf
@@ -0,0 +1,9 @@
+// you can use `less -R filepath.stderr` to see the colored text
+// https://unix.stackexchange.com/questions/262185/display-file-with-ansi-colors
+
+target unknown;
+
+main reactor Foo {
+
+}
+
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/colors.stderr b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/colors.stderr
new file mode 100644
index 0000000000..475f9517f6
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/colors.stderr
@@ -0,0 +1,16 @@
+lfc: error: Unrecognized target: unknown
+--> %%%PATH.lf%%%:4:8
+  |
+3 |
+4 | target unknown;
+  |        ^^^^^^^ Unrecognized target: unknown
+  |
+5 |
+lfc: error: Name of main reactor must match the file name (or be omitted).
+--> %%%PATH.lf%%%:6:14
+  |
+5 |
+6 | main reactor Foo {
+  |              ^^^ Name of main reactor must match the file name (or be omitted).
+  |
+7 |
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/emptyFile.lf b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/emptyFile.lf
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/emptyFile.stderr b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/emptyFile.stderr
new file mode 100644
index 0000000000..f63f06cc5c
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/emptyFile.stderr
@@ -0,0 +1,8 @@
+lfc: error: mismatched input '<EOF>' expecting 'target'
+--> %%%PATH.lf%%%:1:1
+  |
+1 | 
+  | ^ mismatched input '<EOF>' expecting 'target'
+  |
+2 | 
+
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/issue490.lf b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/issue490.lf
new file mode 100644
index 0000000000..2fe700e349
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/issue490.lf
@@ -0,0 +1,9 @@
+# https://github.com/lf-lang/lingua-franca/issues/490
+# issue is that one error ends at EOF
+target Python;
+main reactor R(p(3)) {
+  state liss(2, 3);
+  reaction (startup) {
+    print(self.liss)
+}
+}
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/issue490.stderr b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/issue490.stderr
new file mode 100644
index 0000000000..edf3254755
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/issue490.stderr
@@ -0,0 +1,28 @@
+lfc: error: Name of main reactor must match the file name (or be omitted).
+--> %%%PATH.lf%%%:4:14
+  |
+3 | target Python;
+4 | main reactor R(p(3)) {
+  |              ^ Name of main reactor must match the file name (or be omitted).
+  |
+5 |   state liss(2, 3);
+
+lfc: error: missing '{=' at '{'
+--> %%%PATH.lf%%%:6:22
+  |
+5 |   state liss(2, 3);
+6 |   reaction (startup) {
+  |                      ^ missing '{=' at '{'
+  |
+7 |     print(self.liss)
+
+lfc: error: mismatched input '<EOF>' expecting '=}'
+ --> %%%PATH.lf%%%:9:2
+   |
+ 8 | }
+   | >>>>>>>>>>>>>>
+ 9 | }
+10 | 
+   | < mismatched input '<EOF>' expecting '=}'
+11 | 
+
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/multilineWarning.lf b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/multilineWarning.lf
new file mode 100644
index 0000000000..3d406f1c03
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/multilineWarning.lf
@@ -0,0 +1,5 @@
+target Cpp;
+
+reactor {
+
+}
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/multilineWarning.stderr b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/multilineWarning.stderr
new file mode 100644
index 0000000000..5579a27731
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/multilineWarning.stderr
@@ -0,0 +1,10 @@
+lfc: error: Reactor must be named.
+--> %%%PATH.lf%%%:3:1
+  |
+2 |
+  | >>>>>>>>>>>>>>
+3 | reactor {
+4 |
+5 | }
+  | < Reactor must be named.
+6 |
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/multilineWarningTooBig.lf b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/multilineWarningTooBig.lf
new file mode 100644
index 0000000000..1df335e2f5
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/multilineWarningTooBig.lf
@@ -0,0 +1,13 @@
+target Cpp;
+
+// leading
+reactor {
+    // included 1
+    // excluded
+    // excluded
+    // excluded
+    // excluded
+    // excluded
+    // included 2
+}
+// trailing
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/multilineWarningTooBig.stderr b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/multilineWarningTooBig.stderr
new file mode 100644
index 0000000000..188aa2208f
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/multilineWarningTooBig.stderr
@@ -0,0 +1,12 @@
+lfc: error: Reactor must be named.
+ --> %%%PATH.lf%%%:4:1
+   |
+ 3 | // leading
+   | >>>>>>>>>>>>>>
+ 4 | reactor {
+ 5 |     // included 1
+   | ...
+11 |     // included 2
+12 | }
+   | < Reactor must be named.
+13 | // trailing
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/simpleWarning.lf b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/simpleWarning.lf
new file mode 100644
index 0000000000..0d08ee4fc9
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/simpleWarning.lf
@@ -0,0 +1,5 @@
+target unknown;
+
+main reactor Foo {
+
+}
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/simpleWarning.stderr b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/simpleWarning.stderr
new file mode 100644
index 0000000000..b66665fcfd
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/simpleWarning.stderr
@@ -0,0 +1,16 @@
+lfc: error: Unrecognized target: unknown
+--> %%%PATH.lf%%%:1:8
+  |
+1 | target unknown;
+  |        ^^^^^^^ Unrecognized target: unknown
+  |
+2 |
+
+lfc: error: Name of main reactor must match the file name (or be omitted).
+--> %%%PATH.lf%%%:3:14
+  |
+2 |
+3 | main reactor Foo {
+  |              ^^^ Name of main reactor must match the file name (or be omitted).
+  |
+4 |
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/tabs.lf b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/tabs.lf
new file mode 100644
index 0000000000..43705c8a51
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/tabs.lf
@@ -0,0 +1,6 @@
+target C;
+
+main reactor {
+	state foo(1);
+	state	bar(1);
+}
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/tabs.stderr b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/tabs.stderr
new file mode 100644
index 0000000000..e3b1e765da
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/tabs.stderr
@@ -0,0 +1,16 @@
+lfc: error: State must have a type.
+--> %%%PATH.lf%%%:4:2
+  |
+3 | main reactor {
+4 |     state foo(1);
+  |     ^^^^^^^^^^^^^ State must have a type.
+  |
+5 |     state    bar(1);
+lfc: error: State must have a type.
+--> %%%PATH.lf%%%:5:2
+  |
+4 |     state foo(1);
+5 |     state    bar(1);
+  |     ^^^^^^^^^^^^^^^^ State must have a type.
+  |
+6 | }
\ No newline at end of file
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/twoLineWarning.lf b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/twoLineWarning.lf
new file mode 100644
index 0000000000..ed3790f89d
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/twoLineWarning.lf
@@ -0,0 +1,4 @@
+target Cpp;
+
+ reactor {
+     }
diff --git a/org.lflang.lfc/test/resources/org/lflang/lfc/tests/twoLineWarning.stderr b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/twoLineWarning.stderr
new file mode 100644
index 0000000000..745b863fb7
--- /dev/null
+++ b/org.lflang.lfc/test/resources/org/lflang/lfc/tests/twoLineWarning.stderr
@@ -0,0 +1,9 @@
+lfc: error: Reactor must be named.
+--> %%%PATH.lf%%%:3:2
+  |
+2 |
+  | >>>>>>>>>>>>>>
+3 |  reactor {
+4 |      }
+  | <<<<<< Reactor must be named.
+5 |
diff --git a/org.lflang/src/org/lflang/LFRuntimeModule.java b/org.lflang/src/org/lflang/LFRuntimeModule.java
index 936c5d848a..79a73fd556 100644
--- a/org.lflang/src/org/lflang/LFRuntimeModule.java
+++ b/org.lflang/src/org/lflang/LFRuntimeModule.java
@@ -41,7 +41,7 @@ public Class<? extends INamesAreUniqueValidationHelper> bindNamesAreUniqueValida
     
     public Class<? extends ISyntaxErrorMessageProvider> bindISyntaxErrorMessageProvider() {
         return LFSyntaxErrorMessageProvider.class;
-}
+    }
 
     /** The error reporter. {@link LFStandaloneModule} overrides this binding. */
     public Class<? extends ErrorReporter> bindErrorReporter() {