Improve debug output in case of failing soundsource test

src/test/soundproxy_test.cpp

@@ -125,9 +125,49 @@ class SoundSourceProxyTest : public MixxxTest, SoundSourceProviderRegistration {
             const CSAMPLE* expected,
             const CSAMPLE* actual,
             const char* errorMessage) {
-        for (SINT i = 0; i < size; ++i) {
-            EXPECT_NEAR(expected[i], actual[i], kMaxDecodingError)
-                    << "i=" << i << " " << errorMessage;
+        int error_count = 0;
+        SINT first = 0;
+        SINT last = 0;
+        SINT i = 0;
+        for (; i < size - 1; i += 2) {
+            if (std::abs(expected[i] - actual[i]) > kMaxDecodingError) {
+                error_count = 1;
+                first = i;
+                EXPECT_NEAR(expected[i], actual[i], kMaxDecodingError)
+                        << "i=" << i << " " << errorMessage;
+                break;
+            }
+            if (std::abs(expected[i + 1] - actual[i + 1]) > kMaxDecodingError) {
+                error_count = 1;
+                first = i;
+                EXPECT_NEAR(expected[i + 1], actual[i + 1], kMaxDecodingError)
+                        << "i=" << i << " " << errorMessage;
+                break;
+            }
+        }
+        if (error_count == 1) {
+            std::ostringstream csv;
+            csv << std::setprecision(std::numeric_limits<CSAMPLE>::max_digits10);
+
+            csv << "sep=,\nexpected left,expected right,actual left, actual "
+                   "right, error\n"; // CSV header
+
+            for (SINT i = 0; i < size - 1; i += 2) {
+                csv << expected[i] << "," << expected[i + 1] << "," << actual[i]
+                    << "," << actual[i + 1];
+                if (std::abs(expected[i] - actual[i]) > kMaxDecodingError ||
+                        std::abs(expected[i + 1] - actual[i + 1]) > kMaxDecodingError) {
+                    csv << ",1\n";
+                    error_count++;
+                    last = i;
+                } else {
+                    csv << ",0\n";
+                }
+            }
+            std::cout << "CSV debug output with " << error_count
+                      << " errors in the range " << first / 2 << " to " << last / 2
+                      << ":\n"
+                      << csv.str();
         }
     }
 

src/util/indexrange.cpp

@@ -104,7 +104,7 @@ std::optional<IndexRange> intersect2(IndexRange lhs, IndexRange rhs) {
 }
 
 std::ostream& operator<<(std::ostream& os, IndexRange arg) {
-    return os << '[' << arg.start() << " -> " << arg.end() << ')';
+    return os << '[' << arg.start() << " -> " << arg.end() << ']';
 }
 
 QDebug operator<<(QDebug dbg, IndexRange arg) {